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Aggiunta documentazione di sqlite 3
2020-11-29 00:32:36 +01:00

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Command Line Shell For SQLite
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Table Of Contents
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<div id="toc_sub"><div class="fancy-toc1"><a href="#getting_started">1. Getting Started</a></div>
<div class="fancy-toc1"><a href="#double_click_startup_on_windows">2. Double-click Startup On Windows</a></div>
<div class="fancy-toc1"><a href="#special_commands_to_sqlite3_dot_commands_">3. Special commands to sqlite3 (dot-commands)</a></div>
<div class="fancy-toc1"><a href="#rules_for_dot_commands_">4. Rules for "dot-commands"</a></div>
<div class="fancy-toc1"><a href="#changing_output_formats">5. Changing Output Formats</a></div>
<div class="fancy-toc1"><a href="#writing_results_to_a_file">6. Writing results to a file</a></div>
<div class="fancy-toc2"><a href="#file_i_o_functions">6.1. File I/O Functions</a></div>
<div class="fancy-toc2"><a href="#the_edit_sql_function">6.2. The edit() SQL function</a></div>
<div class="fancy-toc1"><a href="#querying_the_database_schema">7. Querying the database schema</a></div>
<div class="fancy-toc1"><a href="#csv_import">8. CSV Import</a></div>
<div class="fancy-toc1"><a href="#csv_export">9. CSV Export</a></div>
<div class="fancy-toc2"><a href="#_export_to_excel_">9.1. Export to Excel </a></div>
<div class="fancy-toc1"><a href="#accessing_zip_archives_as_database_files">10. Accessing ZIP Archives As Database Files</a></div>
<div class="fancy-toc2"><a href="#how_zip_archive_access_is_implemented">10.1. How ZIP archive access is implemented</a></div>
<div class="fancy-toc1"><a href="#converting_an_entire_database_to_an_ascii_text_file">11. Converting An Entire Database To An ASCII Text File</a></div>
<div class="fancy-toc1"><a href="#recover_data_from_a_corrupted_database">12. Recover Data From a Corrupted Database</a></div>
<div class="fancy-toc1"><a href="#loading_extensions">13. Loading Extensions</a></div>
<div class="fancy-toc1"><a href="#cryptographic_hashes_of_database_content">14. Cryptographic Hashes Of Database Content</a></div>
<div class="fancy-toc1"><a href="#database_content_self_tests">15. Database Content Self-Tests</a></div>
<div class="fancy-toc1"><a href="#sqlite_archive_support">16. SQLite Archive Support</a></div>
<div class="fancy-toc2"><a href="#_sqlite_archive_create_command_">16.1. SQLite Archive Create Command </a></div>
<div class="fancy-toc2"><a href="#_sqlite_archive_extract_command_">16.2. SQLite Archive Extract Command </a></div>
<div class="fancy-toc2"><a href="#_sqlite_archive_list_command_">16.3. SQLite Archive List Command </a></div>
<div class="fancy-toc2"><a href="#_sqlite_archive_insert_and_update_commands_">16.4. SQLite Archive Insert And Update Commands </a></div>
<div class="fancy-toc2"><a href="#_operations_on_zip_archives_">16.5. Operations On ZIP Archives </a></div>
<div class="fancy-toc2"><a href="#_sql_used_to_implement_sqlite_archive_operations_">16.6. SQL Used To Implement SQLite Archive Operations </a></div>
<div class="fancy-toc1"><a href="#sql_parameters">17. SQL Parameters</a></div>
<div class="fancy-toc1"><a href="#index_recommendations_sqlite_expert_">18. Index Recommendations (SQLite Expert)</a></div>
<div class="fancy-toc1"><a href="#other_dot_commands">19. Other Dot Commands</a></div>
<div class="fancy-toc1"><a href="#using_sqlite3_in_a_shell_script">20. Using sqlite3 in a shell script</a></div>
<div class="fancy-toc1"><a href="#ending_shell_commands">21. Ending shell commands</a></div>
<div class="fancy-toc1"><a href="#compiling_the_sqlite3_program_from_sources">22. Compiling the sqlite3 program from sources</a></div>
<div class="fancy-toc2"><a href="#_do_it_yourself_builds_">22.1. Do-It-Yourself Builds </a></div>
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<a name="intro"></a>
<h1 id="getting_started"><span>1. </span>Getting Started</h1>
<p>The SQLite project provides a simple command-line program named
<b>sqlite3</b> (or <b>sqlite3.exe</b> on Windows)
that allows the user to manually enter and execute SQL
statements against an SQLite database or against a
<a href="#zipdb">ZIP archive</a>. This document provides a brief
introduction on how to use the <b>sqlite3</b> program.
</p><p>Start the <b>sqlite3</b> program by typing "sqlite3" at the
command prompt, optionally followed
by the name the file that holds the SQLite database
(or <a href="#zipdb">ZIP archive</a>). If the named
file does not exist, a new database file with the given name will be
created automatically. If no database file is specified on the
command-line, a temporary database is created, then deleted when
the "sqlite3" program exits.
</p><p>On startup, the <b>sqlite3</b> program will show a brief banner
message then prompt you to enter SQL. Type in SQL statements (terminated
by a semicolon), press "Enter" and the SQL will be executed.</p>
<p>For example, to create a new SQLite database named "ex1"
with a single table named "tbl1", you might do this:</p>
<div class="codeblock"><pre>$ <b>sqlite3 ex1</b>
SQLite version 3.28.0 2019-03-02 15:25:24
Enter ".help" for usage hints.
sqlite&gt; <b>create table tbl1(one varchar(10), two smallint);</b>
sqlite&gt; <b>insert into tbl1 values('hello!',10);</b>
sqlite&gt; <b>insert into tbl1 values('goodbye', 20);</b>
sqlite&gt; <b>select * from tbl1;</b>
hello!|10
goodbye|20
sqlite&gt;
</pre></div>
<p>Terminate the sqlite3 program by typing your system
End-Of-File character (usually a Control-D). Use the interrupt
character (usually a Control-C) to stop a long-running SQL statement.</p>
<p>Make sure you type a semicolon at the end of each SQL command!
The sqlite3 program looks for a semicolon to know when your SQL command is
complete. If you omit the semicolon, sqlite3 will give you a
continuation prompt and wait for you to enter more text to be
added to the current SQL command. This feature allows you to
enter SQL commands that span multiple lines. For example:</p>
<div class="codeblock"><pre>sqlite&gt; <b>CREATE TABLE tbl2 (</b>
...&gt; <b> f1 varchar(30) primary key,</b>
...&gt; <b> f2 text,</b>
...&gt; <b> f3 real</b>
...&gt; <b>);</b>
sqlite&gt;
</pre></div>
<a name="dblclick"></a>
<h1 id="double_click_startup_on_windows"><span>2. </span>Double-click Startup On Windows</h1>
<p>Windows users can double-click on the <b>sqlite3.exe</b> icon to cause
the command-line shell to pop-up a terminal window running SQLite. However,
because double-clicking starts the sqlite3.exe without command-line arguments,
no database file will have been specified, so SQLite will use a temporary
database that is deleted when the session exits.
To use a persistent disk file as the database, enter the ".open" command
immediately after the terminal window starts up:
</p><div class="codeblock"><pre>SQLite version 3.28.0 2019-03-02 15:25:24
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database.
sqlite&gt; <b>.open ex1.db</b>
sqlite&gt;
</pre></div>
<p>The example above causes the database file named "ex1.db" to be opened
and used. The "ex1.db" file is created if it does not previously exist.
You might want to
use a full pathname to ensure that the file is in the directory that you
think it is in. Use forward-slashes as the directory separator character.
In other words use "c:/work/ex1.db", not "c:\work\ex1.db".</p>
<p>Alternatively, you can create a new database using the default temporary
storage, then save that database into a disk file using the ".save" command:
</p><div class="codeblock"><pre>SQLite version 3.28.0 2019-03-02 15:25:24
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database.
sqlite&gt; <i>... many SQL commands omitted ...</i>
sqlite&gt; <b>.save ex1.db</b>
sqlite&gt;
</pre></div>
<p>Be careful when using the ".save" command as it will overwrite any
preexisting database files having the same name without prompting for
confirmation. As with the ".open" command, you might want to use a
full pathname with forward-slash directory separators to avoid ambiguity.
<a name="dotcmd"></a>
</p><h1 id="special_commands_to_sqlite3_dot_commands_"><span>3. </span>Special commands to sqlite3 (dot-commands)</h1>
<p>
Most of the time, sqlite3 just reads lines of input and passes them
on to the SQLite library for execution.
But input lines that begin with a dot (".")
are intercepted and interpreted by the sqlite3 program itself.
These "dot commands" are typically used to change the output format
of queries, or to execute certain prepackaged query statements.
There were originally just a few dot commands, but over the years
many new features have accumulated so that today there over 60.
</p>
<p>
For a listing of the available dot commands, you can enter ".help" with
no arguments. Or enter ".help TOPIC" for detailed information about TOPIC.
The list of available dot-commands follows:
</p>
<div class="codeblock"><pre>sqlite&gt; <b>.help</b>
.archive ... Manage SQL archives
.auth ON|OFF Show authorizer callbacks
.backup ?DB? FILE Backup DB (default "main") to FILE
.bail on|off Stop after hitting an error. Default OFF
.binary on|off Turn binary output on or off. Default OFF
.cd DIRECTORY Change the working directory to DIRECTORY
.changes on|off Show number of rows changed by SQL
.check GLOB Fail if output since .testcase does not match
.clone NEWDB Clone data into NEWDB from the existing database
.databases List names and files of attached databases
.dbconfig ?op? ?val? List or change sqlite3_db_config() options
.dbinfo ?DB? Show status information about the database
.dump ?TABLE? Render database content as SQL
.echo on|off Turn command echo on or off
.eqp on|off|full|... Enable or disable automatic EXPLAIN QUERY PLAN
.excel Display the output of next command in spreadsheet
.exit ?CODE? Exit this program with return-code CODE
.expert EXPERIMENTAL. Suggest indexes for queries
.explain ?on|off|auto? Change the EXPLAIN formatting mode. Default: auto
.filectrl CMD ... Run various sqlite3_file_control() operations
.fullschema ?--indent? Show schema and the content of sqlite_stat tables
.headers on|off Turn display of headers on or off
.help ?-all? ?PATTERN? Show help text for PATTERN
.import FILE TABLE Import data from FILE into TABLE
.imposter INDEX TABLE Create imposter table TABLE on index INDEX
.indexes ?TABLE? Show names of indexes
.limit ?LIMIT? ?VAL? Display or change the value of an SQLITE_LIMIT
.lint OPTIONS Report potential schema issues.
.load FILE ?ENTRY? Load an extension library
.log FILE|off Turn logging on or off. FILE can be stderr/stdout
.mode MODE ?TABLE? Set output mode
.nullvalue STRING Use STRING in place of NULL values
.once ?OPTIONS? ?FILE? Output for the next SQL command only to FILE
.open ?OPTIONS? ?FILE? Close existing database and reopen FILE
.output ?FILE? Send output to FILE or stdout if FILE is omitted
.parameter CMD ... Manage SQL parameter bindings
.print STRING... Print literal STRING
.progress N Invoke progress handler after every N opcodes
.prompt MAIN CONTINUE Replace the standard prompts
.quit Exit this program
.read FILE Read input from FILE
.recover Recover as much data as possible from corrupt db.
.restore ?DB? FILE Restore content of DB (default "main") from FILE
.save FILE Write in-memory database into FILE
.scanstats on|off Turn sqlite3_stmt_scanstatus() metrics on or off
.schema ?PATTERN? Show the CREATE statements matching PATTERN
.selftest ?OPTIONS? Run tests defined in the SELFTEST table
.separator COL ?ROW? Change the column and row separators
.sha3sum ... Compute a SHA3 hash of database content
.shell CMD ARGS... Run CMD ARGS... in a system shell
.show Show the current values for various settings
.stats ?on|off? Show stats or turn stats on or off
.system CMD ARGS... Run CMD ARGS... in a system shell
.tables ?TABLE? List names of tables matching LIKE pattern TABLE
.testcase NAME Begin redirecting output to 'testcase-out.txt'
.testctrl CMD ... Run various sqlite3_test_control() operations
.timeout MS Try opening locked tables for MS milliseconds
.timer on|off Turn SQL timer on or off
.trace ?OPTIONS? Output each SQL statement as it is run
.vfsinfo ?AUX? Information about the top-level VFS
.vfslist List all available VFSes
.vfsname ?AUX? Print the name of the VFS stack
.width NUM1 NUM2 ... Set minimum column widths for columnar output
sqlite&gt;
</pre></div>
<a name="dotrules"></a>
<h1 id="rules_for_dot_commands_"><span>4. </span>Rules for "dot-commands"</h1>
<p>Ordinary SQL statements are free-form, and can be
spread across multiple lines, and can have whitespace and
comments anywhere. Dot-commands are
more restrictive:
</p><ul>
<li>A dot-command must begin with the "." at the left margin
with no preceding whitespace.
</li><li>The dot-command must be entirely contained on a single input line.
</li><li>A dot-command cannot occur in the middle of an ordinary SQL
statement. In other words, a dot-command cannot occur at a
continuation prompt.
</li><li>Dot-commands do not recognize comments.
</li></ul>
<p>The dot-commands
are interpreted by the sqlite3.exe command-line program, not by
SQLite itself. So none of the dot-commands will work as an argument
to SQLite interfaces like <a href="c3ref/prepare.html">sqlite3_prepare()</a> or <a href="c3ref/exec.html">sqlite3_exec()</a>.
<a name="dotmode"></a>
</p><h1 id="changing_output_formats"><span>5. </span>Changing Output Formats</h1>
<p>The sqlite3 program is able to show the results of a query
in 14 different formats:
</p><div class="columns" style="columns:8em auto;">
<ul style="padding-top:0;padding-left:4em;">
<li> ascii
</li><li> box
</li><li> csv
</li><li> column
</li><li> html
</li><li> insert
</li><li> json
</li><li> line
</li><li> list
</li><li> markdown
</li><li> quote
</li><li> table
</li><li> tabs
</li><li> tcl
</li></ul></div>
<p>You can use the ".mode" dot command to switch between these output
formats.
>The default output mode is "list". In
list mode, each row of a query result is written on one line of
output and each column within that row is separated by a specific
separator string. The default separator is a pipe symbol ("|").
List mode is especially useful when you are going to send the output
of a query to another program (such as AWK) for additional processing.</p>
<div class="codeblock"><pre>sqlite&gt; <b>.mode list</b>
sqlite&gt; <b>select * from tbl1;</b>
hello|10
goodbye|20
sqlite&gt;
</pre></div>
<p>Use the ".separator" dot command to change the separator.
For example, to change the separator to a comma and
a space, you could do this:</p>
<div class="codeblock"><pre>sqlite&gt; <b>.separator ", "</b>
sqlite&gt; <b>select * from tbl1;</b>
hello, 10
goodbye, 20
sqlite&gt;
</pre></div>
<p>The next ".mode" command will reset the ".separator" back to its default.
So you will need repeat the ".separator" command whenever you change
modes if you want to continue using a non-standard separator.
<a name="dotmodequote"></a>
</p><p>In "quote" mode, the output is formatted as SQL literals. Strings are
enclosed in single-quotes and internal single-quotes are escaped by doubling.
Blobs are displayed in hexadecimal blob literal notation (Ex: x'abcd').
Numbers are displayed as ASCII text and NULL values are shown as "NULL".
All columns are separated from each other by a comma (or whatever alternative
character is selected using ".separator").
</p><div class="codeblock"><pre>sqlite&gt; <b>.mode quote</b>
sqlite&gt; <b>select * from tbl1;</b>
'hello',10
'goodbye',20
sqlite&gt;
</pre></div>
<p>In "line" mode, each column in a row of the database
is shown on a line by itself. Each line consists of the column
name, an equal sign and the column data. Successive records are
separated by a blank line. Here is an example of line mode
output:</p>
<div class="codeblock"><pre>sqlite&gt; <b>.mode line</b>
sqlite&gt; <b>select * from tbl1;</b>
one = hello
two = 10
one = goodbye
two = 20
sqlite&gt;
</pre></div>
<p>In column mode, each record is shown on a separate line with the
data aligned in columns. For example:</p>
<div class="codeblock"><pre>sqlite&gt; <b>.mode column</b>
sqlite&gt; <b>select * from tbl1;</b>
one two
-------- ---
hello 10
goodbye 20
sqlite&gt;
</pre></div>
<p>In "column" mode (and also in "box", "table", and "markdown" modes)
the width of columns adjusts automatically. But you can override this,
providing a minimum width for each column using the ".width" command.
The arguments to ".width" are integers which are the minimum number of
spaces to devote to each column. Negative numbers mean right-justify.
Thus:</p>
<div class="codeblock"><pre>sqlite&gt; <b>.width 12 -6</b>
sqlite&gt; <b>select * from tbl1;</b>
one two
------------ ------
hello! 10
goodbye 20
sqlite&gt;
</pre></div>
<p>A width of 0 means the column width is chosen automatically.
Unspecified columns widths to go zero. Hence, the command
".width" with no arguments sets all columns widths to zero and
hence causes all column widths to be determine automatically.
</p><p>The "column" mode is a tabular output format. Other
tabular output formats as "box", "markdown", and "table":
</p><div class="codeblock"><pre>sqlite&gt; <b>.width</b>
sqlite&gt; <b>.mode markdown</b>
sqlite&gt; <b>select * from tbl1;</b>
| one | two |
|---------|-----|
| hello! | 10 |
| goodbye | 20 |
sqlite&gt; <b>.mode table</b>
sqlite&gt; <b>select * from tbl1;</b>
+---------+-----+
| one | two |
+---------+-----+
| hello! | 10 |
| goodbye | 20 |
+---------+-----+
sqlite&gt; <b>.mode box</b>
sqlite&gt; <b>select * from tbl1;</b>
┌─────────┬─────┐
│ one │ two │
├─────────┼─────┤
│ hello! │ 10 │
│ goodbye │ 20 │
└─────────┴─────┘
sqlite&gt;
</pre></div>
<p>Another useful output mode is "insert". In insert mode, the output
is formatted to look like SQL INSERT statements. Use insert
mode to generate text that can later be used to input data into a
different database.</p>
<p>When specifying insert mode, you have to give an extra argument
which is the name of the table to be inserted into. For example:</p>
<div class="codeblock"><pre>sqlite&gt; <b>.mode insert new_table</b>
sqlite&gt; <b>select * from tbl1;</b>
INSERT INTO "new_table" VALUES('hello',10);
INSERT INTO "new_table" VALUES('goodbye',20);
sqlite&gt;
</pre></div>
<p>Other output modes include "html", "json", and "tcl". Try these
yourself to see what they do.
</p>
<a name="dotoutput"></a>
<h1 id="writing_results_to_a_file"><span>6. </span>Writing results to a file</h1>
<p>By default, sqlite3 sends query results to standard output. You
can change this using the ".output" and ".once" commands. Just put
the name of an output file as an argument to .output and all subsequent
query results will be written to that file. Or use the .once command
instead of .output and output will only be redirected for the single next
command before reverting to the console. Use .output with no arguments to
begin writing to standard output again. For example:</p>
<div class="codeblock"><pre>sqlite&gt; <b>.mode list</b>
sqlite&gt; <b>.separator |</b>
sqlite&gt; <b>.output test_file_1.txt</b>
sqlite&gt; <b>select * from tbl1;</b>
sqlite&gt; <b>.exit</b>
$ <b>cat test_file_1.txt</b>
hello|10
goodbye|20
$
</pre></div>
<p>If the first character of the ".output" or ".once" filename is a pipe
symbol ("|") then the remaining characters are treated as a command and the
output is sent to that command. This makes it easy to pipe the results
of a query into some other process. For example, the
"open -f" command on a Mac opens a text editor to display the content that
it reads from standard input. So to see the results of a query
in a text editor, one could type:</p>
<div class="codeblock"><pre>sqlite3&gt; <b>.once '|open -f'</b>
sqlite3&gt; <b>SELECT * FROM bigTable;</b>
</pre></div>
<p>If the ".output" or ".once" commands have an argument of "-e" then
output is collected into a temporary file and the system text editor is
invoked on that text file. Thus, the command ".once -e" achieves the
same result as ".once '|open -f'" but with the benefit of being portable
across all systems.
</p><p>If the ".output" or ".once" commands have a "-x" argument, that causes
them to accumulate output as Comma-Separated-Values (CSV) in a temporary
file, then invoke the default system utility for viewing CSV files
(usually a spreadsheet program) on the result. This is a quick way of
sending the result of a query to a spreadsheet for easy viewing:
</p><div class="codeblock"><pre>sqlite3&gt; <b>.once -x</b>
sqlite3&gt; <b>SELECT * FROM bigTable;</b>
</pre></div>
<a name="dotexcel"></a>
<p>The ".excel" command is an alias for ".once -x". It does exactly the same
thing.
<a name="fileio"></a>
</p><h2 id="file_i_o_functions"><span>6.1. </span>File I/O Functions</h2>
<p>The command-line shell adds two <a href="appfunc.html">application-defined SQL functions</a> that
facilitate reading content from a file into a table column, and writing the
content of a column into a file, respectively.
</p><p>The readfile(X) SQL function reads the entire content of the file named
X and returns that content as a BLOB. This can be used to load content into
a table. For example:
</p><div class="codeblock"><pre>sqlite&gt; <b>CREATE TABLE images(name TEXT, type TEXT, img BLOB);</b>
sqlite&gt; <b>INSERT INTO images(name,type,img</b>)
...&gt; <b> VALUES('icon','jpeg',readfile('icon.jpg'));</b>
</pre></div>
<p>The writefile(X,Y) SQL function write the blob Y into the file named X
and returns the number of bytes written. Use this function to extract
the content of a single table column into a file. For example:
</p><div class="codeblock"><pre>sqlite&gt; <b>SELECT writefile('icon.jpg',img) FROM images WHERE name='icon';</b>
</pre></div>
<p>Note that the readfile(X) and writefile(X,Y) functions are extension
functions and are not built into the core SQLite library. These routines
are available as a <a href="loadext.html">loadable extension</a> in the
<a href="http://www.sqlite.org/src/artifact?ci=trunk&filename=ext/misc/fileio.c">ext/misc/fileio.c</a>
source file in the <a href="download.html#srctree">SQLite source code repositories</a>.
<a name="editfunc"></a>
</p><h2 id="the_edit_sql_function"><span>6.2. </span>The edit() SQL function</h2>
<p>The CLI has another build-in SQL function named edit(). Edit() takes
one or two arguments. The first argument is a value - usually a large
multi-line string to be edited. The second argument is the name of a
text editor. If the second argument is omitted, the VISUAL environment
variable is used. The edit() function writes its first argument into a
temporary file, invokes the editor on the temporary file, rereads the file
back into memory after the editor is done, then returns the edited text.
</p><p>The edit() function can be used to make changes to large text
values. For example:
</p><div class="codeblock"><pre>sqlite&gt; <b>UPDATE docs SET body=edit(body) WHERE name='report-15';</b>
</pre></div>
<p>In this example, the content of the docs.body field for the entry where
docs.name is "report-15" will be sent to the editor. After the editor returns,
the result will be written back into the docs.body field.
</p><p>The default operation of edit() is to invoke a text editor. But by using
an alternative edit program in the second argument, you can also get it to edit
images or other non-text resources. For example, if you want to modify a JPEG
image that happens to be stored in a field of a table, you could run:
</p><div class="codeblock"><pre>sqlite&gt; <b>UPDATE pics SET img=edit(img,'gimp') WHERE id='pic-1542';</b>
</pre></div>
<p>The edit program can also be used as a viewer, by simply ignoring the
return value. For example, to merely look at the image above, you might run:
</p><div class="codeblock"><pre>sqlite&gt; <b>SELECT length(edit(img,'gimp')) WHERE id='pic-1542';</b>
</pre></div>
<a name="schema"></a>
<h1 id="querying_the_database_schema"><span>7. </span>Querying the database schema</h1>
<p>The sqlite3 program provides several convenience commands that
are useful for looking at the schema of the database. There is
nothing that these commands do that cannot be done by some other
means. These commands are provided purely as a shortcut.</p>
<a name="dtables"></a>
<p>For example, to see a list of the tables in the database, you
can enter ".tables".</p>
<div class="codeblock"><pre>sqlite&gt; <b>.tables</b>
tbl1
tbl2
sqlite&gt;
</pre></div>
<p>The ".tables" command is similar to setting list mode then
executing the following query:</p>
<div class="codeblock"><pre>SELECT name FROM sqlite_schema
WHERE type IN ('table','view') AND name NOT LIKE 'sqlite_%'
ORDER BY 1
</pre></div>
<p>But the ".tables" command does more. It queries the <a href="schematab.html">sqlite_schema</a> table
for all <a href="lang_attach.html">attached</a> databases, not just the primary database. And it arranges
its output into neat columns.
</p><p>The ".indexes" command works in a similar way to list all of
the indexes. If the ".indexes" command is given an argument which is
the name of a table, then it shows just indexes on that table.
<a name="dschema"></a>
</p><p>The ".schema" command shows the complete schema for the database,
or for a single table if an optional tablename argument is provided:
</p><div class="codeblock"><pre>sqlite&gt; <b>.schema</b>
create table tbl1(one varchar(10), two smallint)
CREATE TABLE tbl2 (
f1 varchar(30) primary key,
f2 text,
f3 real
)
sqlite&gt; <b>.schema tbl2</b>
CREATE TABLE tbl2 (
f1 varchar(30) primary key,
f2 text,
f3 real
)
sqlite&gt;
</pre></div>
<p>The ".schema" command is roughly the same as setting
list mode, then entering the following query:</p>
<div class="codeblock"><pre>SELECT sql FROM sqlite_schema
ORDER BY tbl_name, type DESC, name
</pre></div>
<p>As with ".tables", the ".schema" command shows the schema for
all <a href="lang_attach.html">attached</a> databases. If you only want to see the schema for
a single database (perhaps "main") then you can add an argument
to ".schema" to restrict its output:
</p><div class="codeblock"><pre>sqlite&gt; <b>.schema main.*</b>
</pre></div>
<p>The ".schema" command can be augmented with the "--indent" option,
in which case it tries to reformat the various CREATE statements of
the schema so that they are more easily readable by humans.
</p><p>The ".databases" command shows a list of all databases open in
the current connection. There will always be at least 2. The first
one is "main", the original database opened. The second is "temp",
the database used for temporary tables. There may be additional
databases listed for databases attached using the ATTACH statement.
The first output column is the name the database is attached with,
and the second column is the filename of the external file.</p>
<div class="codeblock"><pre>sqlite&gt; <b>.databases</b>
</pre></div>
<a name="fullschema"></a>
<p>The ".fullschema" dot-command works like the ".schema" command in
that it displays the entire database schema. But ".fullschema" also
includes dumps of the statistics tables "sqlite_stat1", "sqlite_stat3",
and "sqlite_stat4", if they exist. The ".fullschema" command normally
provides all of the information needed to exactly recreate a query
plan for a specific query. When reporting suspected problems with
the SQLite query planner to the SQLite development team, developers
are requested to provide the complete ".fullschema" output as part
of the trouble report. Note that the sqlite_stat3 and sqlite_stat4
tables contain samples of index entries and so might contain sensitive
data, so do not send the ".fullschema" output of a proprietary database
over a public channel.</p>
<a name="csv"></a>
<h1 id="csv_import"><span>8. </span>CSV Import</h1>
<p>Use the ".import" command to import CSV (comma separated value) data into
an SQLite table. The ".import" command takes two arguments which are the
name of the disk file from which CSV data is to be read and the name of the
SQLite table into which the CSV data is to be inserted.
</p><p>Note that it is important to set the "mode" to "csv" before running the
".import" command. This is necessary to prevent the command-line shell
from trying to interpret the input file text as some other format.
</p><div class="codeblock"><pre>sqlite&gt; <b>.import C:/work/somedata.csv tab1</b>
</pre></div>
<p>There are two cases to consider: (1) Table "tab1" does not previously
exist and (2) table "tab1" does already exist.
</p><p>In the first case, when the table does not previously exist, the table is
automatically created and the content of the first row of the input CSV
file is used to determine the name of all the columns in the table. In
other words, if the table does not previously exist, the first row of the
CSV file is interpreted to be column names and the actual data starts on
the second row of the CSV file.
</p><p>For the second case, when the table already exists, every row of the
CSV file, including the first row, is assumed to be actual content. If
the CSV file contains an initial row of column labels, you can cause
the .import command to skip that initial row using the "--skip 1" option.
<a name="csvout"></a>
</p><h1 id="csv_export"><span>9. </span>CSV Export</h1>
<p>To export an SQLite table (or part of a table) as CSV, simply set
the "mode" to "csv" and then run a query to extract the desired rows
of the table.
</p><div class="codeblock"><pre>sqlite&gt; <b>.headers on</b>
sqlite&gt; <b>.mode csv</b>
sqlite&gt; <b>.once c:/work/dataout.csv</b>
sqlite&gt; <b>SELECT * FROM tab1;</b>
sqlite&gt; <b>.system c:/work/dataout.csv</b>
</pre></div>
<p>In the example above, the ".headers on" line causes column labels to
be printed as the first row of output. This means that the first row of
the resulting CSV file will contain column labels. If column labels are
not desired, set ".headers off" instead. (The ".headers off" setting is
the default and can be omitted if the headers have not been previously
turned on.)
</p><p>The line ".once <i>FILENAME</i>" causes all query output to go into
the named file instead of being printed on the console. In the example
above, that line causes the CSV content to be written into a file named
"C:/work/dataout.csv".
</p><p>The final line of the example (the ".system c:/work/dataout.csv")
has the same effect as double-clicking on the c:/work/dataout.csv file
in windows. This will typically bring up a spreadsheet program to display
the CSV file.
</p><p>That command only works as written on Windows.
The equivalent line on a Mac would be:
</p><div class="codeblock"><pre>sqlite&gt; <b>.system open dataout.csv</b>
</pre></div>
<p>On Linux and other unix systems you will need to enter something like:
</p><div class="codeblock"><pre>sqlite&gt; <b>.system xdg-open dataout.csv</b>
</pre></div>
<a name="exexcel*"></a>
<h2 id="_export_to_excel_"><span>9.1. </span> Export to Excel </h2>
<p>To simplify export to a spreadsheet, the CLI provides the
".excel" command which captures the output of a single query and sends
that output to the default spreadsheet program on the host computer.
Use it like this:
</p><div class="codeblock"><pre>sqlite&gt; <b>.excel</b>
sqlite&gt; <b>SELECT * FROM tab;</b>
</pre></div>
<p>
The command above writes the output of the query as CSV into a temporary
file, invokes the default handler for CSV files (usually the preferred
spreadsheet program such as Excel or LibreOffice), then deletes the
temporary file. This is essentially a short-hand method of doing
the sequence of ".csv", ".once", and ".system" commands described above.
</p><p>
The ".excel" command is really an alias for ".once -x". The -x option
to .once causes it to writes results as CSV into a temporary file that
is named with a ".csv" suffix, then invoke the systems default handler
for CSV files.
</p><p>
There is also a ".once -e" command which works similarly, except that
it names the temporary file with a ".txt" suffix so that the default
text editor for the system will be invoked, instead of the default
spreadsheet.
<a name="zipdb"></a>
</p><h1 id="accessing_zip_archives_as_database_files"><span>10. </span>Accessing ZIP Archives As Database Files</h1>
<p>In addition to reading and writing SQLite database files,
the <b>sqlite3</b> program will also read and write ZIP archives.
Simply specify a ZIP archive filename in place of an SQLite database
filename on the initial command line, or in the ".open" command,
and <b>sqlite3</b> will automatically detect that the file is a
ZIP archive instead of an SQLite database and will open it as such.
This works regardless of file suffix. So you can open JAR, DOCX,
and ODP files and any other file format that is really a ZIP
archive and SQLite will read it for you.
</p><p>A ZIP archive appears to be a database containing a single table
with the following schema:
</p><div class="codeblock"><pre>CREATE TABLE zip(
name, // Name of the file
mode, // Unix-style file permissions
mtime, // Timestamp, seconds since 1970
sz, // File size after decompression
rawdata, // Raw compressed file data
data, // Uncompressed file content
method // ZIP compression method code
);
</pre></div>
<p>So, for example, if you wanted to see the compression efficiency
(expressed as the size of the compressed content relative to the
original uncompressed file size) for all files in the ZIP archive,
sorted from most compressed to least compressed, you could run a
query like this:
</p><div class="codeblock"><pre>sqlite&gt; SELECT name, (100.0*length(rawdata))/sz FROM zip ORDER BY 2;
</pre></div>
<p>Or using <a href="cli.html#fileio">file I/O functions</a>, you can extract elements of the
ZIP archive:
</p><div class="codeblock"><pre>sqlite&gt; SELECT writefile(name,content) FROM zip
...&gt; WHERE name LIKE 'docProps/%';
</pre></div>
<h2 id="how_zip_archive_access_is_implemented"><span>10.1. </span>How ZIP archive access is implemented</h2>
<p>The command-line shell uses the <a href="zipfile.html">Zipfile virtual table</a> to
access ZIP archives. You can see this by running the ".schema"
command when a ZIP archive is open:
</p><div class="codeblock"><pre>sqlite&gt; .schema
CREATE VIRTUAL TABLE zip USING zipfile('document.docx')
/* zip(name,mode,mtime,sz,rawdata,data,method) */;
</pre></div>
<p>When opening a file, if the command-line client discovers that the
file is ZIP archive instead of an SQLite database, it actually opens
an <a href="inmemorydb.html">in-memory database</a> and then in that in-memory database it creates
an instance of the <a href="zipfile.html">Zipfile virtual table</a> that is attached to the
ZIP archive.
</p><p>The special processing for opening ZIP archives is a trick of the
command-line shell, not the core SQLite library. So if you want to
open a ZIP archive as a database in your application, you will need to
activate the <a href="zipfile.html">Zipfile virtual table</a> module then run an appropriate
<a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> statement.
<a name="dump"></a>
</p><h1 id="converting_an_entire_database_to_an_ascii_text_file"><span>11. </span>Converting An Entire Database To An ASCII Text File</h1>
<p>Use the ".dump" command to convert the entire contents of a
database into a single ASCII text file. This file can be converted
back into a database by piping it back into <b>sqlite3</b>.</p>
<p>A good way to make an archival copy of a database is this:</p>
<div class="codeblock"><pre>$ <b>sqlite3 ex1 .dump | gzip -c &gt;ex1.dump.gz</b>
</pre></div>
<p>This generates a file named <b>ex1.dump.gz</b> that contains everything
you need to reconstruct the database at a later time, or on another
machine. To reconstruct the database, just type:</p>
<div class="codeblock"><pre>$ <b>zcat ex1.dump.gz | sqlite3 ex2</b>
</pre></div>
<p>The text format is pure SQL so you
can also use the .dump command to export an SQLite database
into other popular SQL database engines. Like this:</p>
<div class="codeblock"><pre>$ <b>createdb ex2</b>
$ <b>sqlite3 ex1 .dump | psql ex2</b>
</pre></div>
<a name="recover"></a>
<h1 id="recover_data_from_a_corrupted_database"><span>12. </span>Recover Data From a Corrupted Database</h1>
<p>Like the ".dump" command, ".recover" attempts to convert the entire
contents of a database file to text. The difference is that instead of
reading data using the normal SQL database interface, ".recover"
attempts to reassemble the database based on data extracted directly from
as many database pages as possible. If the database is corrupt, ".recover"
is usually able to recover data from all uncorrupted parts of the database,
whereas ".dump" stops when the first sign of corruption is encountered.
</p><p>If the ".recover" command recovers one or more rows that it cannot
attribute to any database table, the output script creates a "lost_and_found"
table to store the orphaned rows. The schema of the lost_and_found
table is as follows:
</p><div class="codeblock"><pre>CREATE TABLE lost_and_found(
rootpgno INTEGER, -- root page of tree pgno is a part of
pgno INTEGER, -- page number row was found on
nfield INTEGER, -- number of fields in row
id INTEGER, -- value of rowid field, or NULL
c0, c1, c2, c3... -- columns for fields of row
);
</pre></div>
<p>The "lost_and_found" table contains one row for each orphaned row recovered
from the database. Additionally, there is one row for each recovered index
entry that cannot be attributed to any SQL index. This is because, in an
SQLite database, the same format is used to store SQL index entries and
WITHOUT ROWID table entries.
</p><table striped="1" style="margin:1em auto; width:80%; border-spacing:0">
<tr style="text-align:left"><th style="width:15ex">Column</th><th>Contents
</th></tr><tr style="text-align:left;background-color:#DDDDDD"><td>rootpgno</td><td> Even though it may not be possible to attribute the
row to a specific database table, it may be part of a tree structure
within the database file. In this case, the root page number of that
tree structure is stored in this column. Or, if the page the row was
found on is not part of a tree structure, this column stores a copy of
the value in column "pgno" - the page number of the page the row was
found on. In many, although not all, cases, all rows in the
lost_and_found table with the same value in this column belong to the
same table.
</td></tr><tr style="text-align:left"><td>pgno</td><td> The page number of the page on which this row was found.
</td></tr><tr style="text-align:left;background-color:#DDDDDD"><td>nfield</td><td> The number of fields in this row.
</td></tr><tr style="text-align:left"><td>id</td><td> If the row comes from a WITHOUT ROWID table, this column
contains NULL. Otherwise, it contains the 64-bit integer rowid value for
the row.
</td></tr><tr style="text-align:left;background-color:#DDDDDD"><td>c0,&nbsp;c1,&nbsp;c2...</td><td> The values for each column of the row
are stored in these columns. The ".recover" command creates the
lost_and_found table with as many columns as required by the longest
orphaned row.
</td></tr></table>
<p>If the recovered database schema already contains a table named
"lost_and_found", the ".recover" command uses the name "lost_and_found0". If
the name "lost_and_found0" is also already taken, "lost_and_found1", and so
on. The default name "lost_and_found" may be overridden by invoking ".recover"
with the --lost-and-found switch. For example, to have the output script call
the table "orphaned_rows":
</p><div class="codeblock"><pre>sqlite&gt; .recover --lost-and-found orphaned_rows
</pre></div>
<a name="dotload"></a>
<h1 id="loading_extensions"><span>13. </span>Loading Extensions</h1>
<p>You can add new custom <a href="appfunc.html">application-defined SQL functions</a>,
<a href="datatype3.html#collation">collating sequences</a>, <a href="vtab.html">virtual tables</a>, and <a href="vfs.html">VFSes</a> to the command-line
shell at run-time using the ".load" command. First, convert the
extension in to a DLL or shared library (as described in the
<a href="loadext.html">Run-Time Loadable Extensions</a> document) then type:
</p><div class="codeblock"><pre>sqlite&gt; .load /path/to/my_extension
</pre></div>
<p>Note that SQLite automatically adds the appropriate extension suffix
(".dll" on windows, ".dylib" on Mac, ".so" on most other unixes) to the
extension filename. It is generally a good idea to specify the full
pathname of the extension.
</p><p>SQLite computes the entry point for the extension based on the extension
filename. To override this choice, simply add the name of the extension
as a second argument to the ".load" command.
</p><p>Source code for several useful extensions can be found in the
<a href="http://www.sqlite.org/src/tree?name=ext/misc&ci=trunk">ext/misc</a>
subdirectory of the SQLite source tree. You can use these extensions
as-is, or as a basis for creating your own custom extensions to address
your own particular needs.
<a name="sha3sum"></a>
</p><h1 id="cryptographic_hashes_of_database_content"><span>14. </span>Cryptographic Hashes Of Database Content</h1>
<p>The ".sha3sum" dot-command computes a
<a href="https://en.wikipedia.org/wiki/SHA-3">SHA3</a> hash of the <em>content</em>
of the database. To be clear, the hash is computed over the database content,
not its representation on disk. This means, for example, that a <a href="lang_vacuum.html">VACUUM</a>
or similar data-preserving transformation does not change the hash.
</p><p>The ".sha3sum" command supports options "--sha3-224", "--sha3-256",
"--sha3-384", and "--sha3-512" to define which variety of SHA3 to use
for the hash. The default is SHA3-256.
</p><p>The database schema (in the <a href="schematab.html">sqlite_schema</a> table) is not normally
included in the hash, but can be added by the "--schema" option.
</p><p>The ".sha3sum" command takes a single optional argument which is a
<a href="lang_expr.html#like">LIKE</a> pattern. If this option is present, only tables whose names match
the <a href="lang_expr.html#like">LIKE</a> pattern will be hashed.
</p><p>The ".sha3sum" command is implemented with the help of the
<a href="https://www.sqlite.org/src/file/ext/misc/shathree.c">extension function "sha3_query()"</a>
that is included with the command-line shell.
<a name="selftest"></a>
</p><h1 id="database_content_self_tests"><span>15. </span>Database Content Self-Tests</h1>
<p>The ".selftest" command attempts to verify that a database is
intact and is not corrupt.
The .selftest command looks for a table in schema named "selftest"
and defined as follows:
</p><div class="codeblock"><pre>CREATE TABLE selftest(
tno INTEGER PRIMARY KEY, -- Test number
op TEXT, -- 'run' or 'memo'
cmd TEXT, -- SQL command to run, or text of "memo"
ans TEXT -- Expected result of the SQL command
);
</pre></div>
<p>The .selftest command reads the rows of the selftest table in
selftest.tno order.
For each 'memo' row, it writes the text in 'cmd' to the output. For
each 'run' row, it runs the 'cmd' text as SQL and compares the result
to the value in 'ans', and shows an error message if the results differ.
</p><p>If there is no selftest table, the ".selftest" command runs
<a href="pragma.html#pragma_integrity_check">PRAGMA integrity_check</a>.
</p><p>The ".selftest --init" command creates the selftest table if it
does not already exists, then appends entries that check the SHA3
hash of the content of all tables. Subsequent runs of ".selftest"
will verify that the database has not been changed in any way. To
generates tests to verify that a subset of the tables are unchanged,
simply run ".selftest --init" then <a href="lang_delete.html">DELETE</a> the selftest rows that
refer to tables that are not constant.
<a name="sqlar"></a>
</p><h1 id="sqlite_archive_support"><span>16. </span>SQLite Archive Support</h1>
<p>The ".archive" dot-command and the "-A" command-line option
provide built-in support for the
<a href="sqlar.html">SQLite Archive format</a>. The interface is similar to
that of the "tar" command on unix systems. Each invocation of the ".ar"
command must specify a single command option. The following commands
are available for ".archive":
</p><table striped="1" style="margin:1em auto; width:80%; border-spacing:0">
<tr style="text-align:left"><th style="width:15ex">Option</th><th style="width:17ex">Long&nbsp;Option</th><th>Purpose
</th></tr><tr style="text-align:left;background-color:#DDDDDD"><td>-c</td><td>--create</td><td>Create a new archive containing specified files.
</td></tr><tr style="text-align:left"><td>-x</td><td>--extract</td><td>Extract specified files from archive.
</td></tr><tr style="text-align:left;background-color:#DDDDDD"><td>-i</td><td>--insert</td><td>Add files to existing archive.
</td></tr><tr style="text-align:left"><td>-t</td><td>--list</td><td>List the files in the archive.
</td></tr><tr style="text-align:left;background-color:#DDDDDD"><td>-u</td><td>--update</td><td>Add files to existing archive <em>if</em> they have changed.
</td></tr></table>
<p>As well as the command option, each invocation of ".ar" may specify
one or more modifier options. Some modifier options require an argument,
some do not. The following modifier options are available:
</p><table striped="1" style="margin:1em auto; width:80%; border-spacing:0">
<tr style="text-align:left"><th style="width:15ex">Option</th><th style="width:17ex">Long&nbsp;Option</th><th>Purpose
</th></tr><tr style="text-align:left;background-color:#DDDDDD"><td>-v</td><td>--verbose</td><td>List each file as it is processed.
</td></tr><tr style="text-align:left"><td>-f FILE</td><td>--file FILE</td><td>If specified, use file FILE as the
archive. Otherwise, assume that the current "main" database is the
archive to be operated on.
</td></tr><tr style="text-align:left;background-color:#DDDDDD"><td>-a FILE</td><td>--append FILE</td><td>Like --file, use file FILE as the
archive, but open the file using the
<a href="https://sqlite.org/src/file/ext/misc/appendvfs.c">apndvfs VFS</a> so that
the archive will be appended to the end of FILE if FILE already exists.
</td></tr><tr style="text-align:left"><td>-C DIR</td><td>--directory DIR</td><td>If specified, interpret all relative
paths as relative to DIR, instead of the current working directory.
</td></tr><tr style="text-align:left;background-color:#DDDDDD"><td>-n</td><td>--dryrun</td><td>Show the SQL that would be run to carry out the
archive operation, but do not actually change anything.
</td></tr><tr style="text-align:left"><td>--</td><td>--</td><td>All subsequent command line words are command arguments,
not options.
</td></tr></table>
<p>
For command-line usage, add the short style command-line options immediately
following the "-A", without an intervening space. All subsequent arguments
are considered to be part of the .archive command. For example, the following
commands are equivalent:
</p><div class="codeblock"><pre>sqlite3 new_archive.db -Acv file1 file2 file3
sqlite3 new_archive.db ".ar -cv file1 file2 file3"
</pre></div>
<p>
Long and short style options may be mixed. For example, the following are
equivalent:
</p><div class="codeblock"><pre><i>-- Two ways to create a new archive named "new_archive.db" containing</i>
<i>-- files "file1", "file2" and "file3".</i>
.ar -c --file new_archive.db file1 file2 file3
.ar -f new_archive.db --create file1 file2 file3
</pre></div>
<p>Alternatively, the first argument following to ".ar" may be the concatenation
of the short form of all required options (without the "-" characters). In
this case arguments for options requiring them are read from the command line
next, and any remaining words are considered command arguments. For example:
</p><div class="codeblock"><pre><i>-- Create a new archive "new_archive.db" containing files "file1" and</i>
<i>-- "file2" from directory "dir1".</i>
.ar cCf dir1 new_archive.db file1 file2 file3
</pre></div>
<h2 id="_sqlite_archive_create_command_"><span>16.1. </span> SQLite Archive Create Command </h2>
<p>Create a new archive, overwriting any existing archive (either in the current
"main" db or in the file specified by a --file option). Each argument following
the options is a file to add to the archive. Directories are imported
recursively. See above for examples.
</p><h2 id="_sqlite_archive_extract_command_"><span>16.2. </span> SQLite Archive Extract Command </h2>
<p>Extract files from the archive (either to the current working directory or
to the directory specified by a --directory option). If there are no arguments
following the options all files are extracted from the archive. Or, if there
are arguments, they are the names of files to extract from the archive. Any
specified directories are extracted recursively. It is an error if any
specified files are not part of the archive.
</p><div class="codeblock"><pre><i>-- Extract all files from the archive in the current "main" db to the</i>
<i>-- current working directory. List files as they are extracted. </i>
.ar --extract --verbose
<i>-- Extract file "file1" from archive "ar.db" to directory "dir1".</i>
.ar fCx ar.db dir1 file1
</pre></div>
<h2 id="_sqlite_archive_list_command_"><span>16.3. </span> SQLite Archive List Command </h2>
<p>List the contents of the archive. If no arguments are specified, then all
files are listed. Otherwise, only those specified as arguments are. Currently,
the --verbose option does not change the behaviour of this command. That may
change in the future.
</p><div class="codeblock"><pre><i>-- List contents of archive in current "main" db.</i>.
.ar --list
</pre></div>
<a name="arinsup"></a>
<h2 id="_sqlite_archive_insert_and_update_commands_"><span>16.4. </span> SQLite Archive Insert And Update Commands </h2>
<p> The --update and --insert commands work like --create command, except that
they do not delete the current archive before commencing. New versions of
files silently replace existing files with the same names, but otherwise
the initial contents of the archive (if any) remain intact.
</p><p> For the --insert command, all files listed are inserted into the archive.
For the --update command, files are only inserted if they do not previously
exist in the archive, or if their "mtime" or "mode" is different from what
is currently in the archive.
</p><p> Compatibility node: Prior to SQLite version 3.28.0 (2019-04-16) only
the --update option was supported but that option worked like --insert in that
it always reinserted every file regardless of whether or not it had changed.
</p><h2 id="_operations_on_zip_archives_"><span>16.5. </span> Operations On ZIP Archives </h2>
<p>If FILE is a ZIP archive rather than an SQLite Archive, the ".archive"
command and the "-A" command-line option still work. This is accomplished
using of the <a href="zipfile.html">zipfile</a> extension.
Hence, the following commands are roughly equivalent,
differing only in output formatting:
</p><table striped="1" style="margin:1em auto; width:80%; border-spacing:0">
<tr style="text-align:left"><th>Traditional Command</th><th>Equivalent sqlite3.exe Command
</th></tr><tr style="text-align:left;background-color:#DDDDDD"><td>unzip archive.zip</td><td>sqlite3 -Axf archive.zip
</td></tr><tr style="text-align:left"><td>unzip -l archive.zip</td><td>sqlite3 -Atvf archive.zip
</td></tr><tr style="text-align:left;background-color:#DDDDDD"><td>zip -r archive2.zip dir</td><td>sqlite3 -Acf archive2.zip dir
</td></tr></table>
<h2 id="_sql_used_to_implement_sqlite_archive_operations_"><span>16.6. </span> SQL Used To Implement SQLite Archive Operations </h2>
<p>The various SQLite Archive Archive commands are implemented using SQL statements.
Application developers can easily add SQLite Archive Archive reading and writing
support to their own projects by running the appropriate SQL.
</p><p>To see what SQL statements are used to implement an SQLite Archive
operation, add the --dryrun or -n option. This causes the SQL to be
displayed but inhibits the execution of the SQL.
</p><p>The SQL statements used to implement SQLite Archive operations make use of
various <a href="loadext.html">loadable extensions</a>. These extensions are all available in
the <a href="https://sqlite.org/src">SQLite source tree</a> in the
<a href="https://sqlite.org/src/file/ext/misc">ext/misc/ subfolder</a>.
The extensions needed for full SQLite Archive support include:
</p><ol>
<li><p>
<a href="https://sqlite.org/src/file/ext/misc/fileio.c">fileio.c</a> &mdash;
This extension adds SQL functions readfile() and writefile() for
reading and writing content from files on disk. The fileio.c
extension also includes fsdir() table-valued function for listing
the contents of a directory and the lsname() function for converting
numeric st_mode integers from the stat() system call into human-readable
strings after the fashion of the "ls -l" command.
</p></li><li><p>
<a href="https://sqlite.org/src/file/ext/misc/sqlar.c">sqlar.c</a> &mdash;
This extension adds the sqlar_compress() and sqlar_uncompress()
functions that are needed to compress and uncompress file content
as it is insert and extracted from an SQLite Archive.
</p></li><li><p>
<a href="zipfile.html">zipfile.c</a> &mdash;
This extension implements the "zipfile(FILE)" table-valued function
which is used to read ZIP archives. This extension is only needed
when reading ZIP archives instead of SQLite archives.
</p></li><li><p>
<a href="https://sqlite.org/src/file/ext/misc/appendvfs.c">appendvfs.c</a> &mdash;
This extension implements a new <a href="vfs.html">VFS</a> that allows an SQLite database
to be appended to some other file, such as an executable. This
extension is only needed if the --append option to the .archive
command is used.
</p></li></ol>
<a name="param"></a>
<h1 id="sql_parameters"><span>17. </span>SQL Parameters</h1>
<p>SQLite allows <a href="lang_expr.html#varparam">bound parameters</a> to appear in an SQL statement anywhere
that a literal value is allowed. The values for these parameters are set
using the <a href="c3ref/bind_blob.html">sqlite3_bind_...()</a> family of APIs.
</p><p>Parameters can be either named or unnamed. An unnamed parameter is a single
question mark ("?"). Named parameters are a "?" followed immediately by a number
(ex: "?15" or "?123") or one of the characters "$", ":", or "@" followed by an
alphanumeric name (ex: "$var1", ":xyz", "@bingo").
</p><p>This command-line shell leaves unnamed parameters unbound, meaning that they
will have a value of an SQL NULL, but named parameters might be assigned values.
If there exists a TEMP table named "sqlite_parameters" with a schema like this:
</p><div class="codeblock"><pre>CREATE TEMP TABLE sqlite_parameters(
key TEXT PRIMARY KEY,
value ANY
) WITHOUT ROWID;
</pre></div>
<p>And if there is an entry in that table where the key column exactly matches
the name of parameter (including the initial "?", "$", ":", or "@" character)
then the parameter is assigned the value of the value column. If no entry exists,
the parameter defaults to NULL.
</p><p>The ".parameter" command exists to simplify managing this table. The
".parameter init" command (often abbreviated as just ".param init") creates
the temp.sqlite_parameters table if it does not already exist. The ".param list"
command shows all entries in the temp.sqlite_parameters table. The ".param clear"
command drops the temp.sqlite_parameters table. The ".param set KEY VALUE" and
".param unset KEY" commands create or delete entries from the
temp.sqlite_parameters table.
</p><p>The temp.sqlite_parameters table only provides values for parameters in the
command-line shell. The temp.sqlite_parameter table has no effect on queries
that are run directly using the SQLite C-language API. Individual applications
are expected to implement their own parameter binding. You can search for
"sqlite_parameters" in the
<a href="https://sqlite.org/src/file/src/shell.c.in">command-line shell source code</a>
to see how the command-line shell does parameter binding, and use that as
a hint for how to implement it yourself.
<a name="expert"></a>
</p><h1 id="index_recommendations_sqlite_expert_"><span>18. </span>Index Recommendations (SQLite Expert)</h1>
<p><b>Note: This command is experimental. It may be removed or the
interface modified in incompatible ways at some point in the future.
</b></p><p>For most non-trivial SQL databases, the key to performance is creating
the right SQL indexes. In this context "the right SQL indexes" means those
that cause the queries that an application needs to optimize run fast. The
".expert" command can assist with this by proposing indexes that might
assist with specific queries, were they present in the database.
</p><p>The ".expert" command is issued first, followed by the SQL query
on a separate line. For example, consider the following session:
</p><div class="codeblock"><pre>sqlite&gt; CREATE TABLE x1(a, b, c); <i>-- Create table in database </i>
sqlite&gt; .expert
sqlite&gt; SELECT * FROM x1 WHERE a=? AND b&gt;?; <i>-- Analyze this SELECT </i>
CREATE INDEX x1_idx_000123a7 ON x1(a, b);
0|0|0|SEARCH TABLE x1 USING INDEX x1_idx_000123a7 (a=? AND b&gt;?)
sqlite&gt; CREATE INDEX x1ab ON x1(a, b); <i>-- Create the recommended index </i>
sqlite&gt; .expert
sqlite&gt; SELECT * FROM x1 WHERE a=? AND b&gt;?; <i>-- Re-analyze the same SELECT </i>
(no new indexes)
0|0|0|SEARCH TABLE x1 USING INDEX x1ab (a=? AND b&gt;?)
</pre></div>
<p>In the above, the user creates the database schema (a single table - "x1"),
and then uses the ".expert" command to analyze a query, in this case
"SELECT * FROM x1 WHERE a=? AND b&gt;?". The shell tool recommends that the
user create a new index (index "x1_idx_000123a7") and outputs the plan
that the query would use in <a href="eqp.html">EXPLAIN QUERY PLAN</a> format. The user then creates
an index with an equivalent schema and runs the analysis on the same query
again. This time the shell tool does not recommend any new indexes, and
outputs the plan that SQLite will use for the query given the existing
indexes.
</p><p>The ".expert" command accepts the following options:
</p><table striped="1" style="margin:1em auto; width:80%; border-spacing:0">
<tr style="text-align:left"><th> Option </th><th> Purpose
</th></tr><tr style="text-align:left;background-color:#DDDDDD"><td> --verbose
</td><td> If present, output a more verbose report for each query analyzed.
</td></tr><tr style="text-align:left"><td> --sample&nbsp;PERCENT
</td><td> By default, the ".expert" command recommends indexes based on the
query and database schema alone. This is similar to the way the
<a href="optoverview.html">SQLite query planner</a> selects indexes for queries if the user has not
run the <a href="lang_analyze.html">ANALYZE</a> command on the database to generate data
distribution statistics.
<div style="margin-top:1ex">
If this option is passed a non-zero argument, the ".expert" command
generates similar data distribution statistics for all indexes
considered based on PERCENT percent of the rows currently stored in
each database table. For databases with unusual data distributions,
this may lead to better index recommendations, particularly if the
application intends to run ANALYZE.
<div style="margin-top:1ex">
For small databases and modern CPUs, there is usually no reason not
to pass "--sample 100". However, gathering data distribution
statistics can be expensive for large database tables. If the
operation is too slow, try passing a smaller value for the --sample
option.
</div></div></td></tr></table>
<p>Th functionality described in this section may be integrated into other
applications or tools using the
<a href="http://www.sqlite.org/src/dir?ci=trunk&name=ext/expert">
SQLite expert extension</a> code.
<a name="dotother"></a>
</p><h1 id="other_dot_commands"><span>19. </span>Other Dot Commands</h1>
<p>There are many other dot-commands available in the command-line
shell. See the ".help" command for a complete list for any particular
version and build of SQLite.
<a name="insh"></a>
</p><h1 id="using_sqlite3_in_a_shell_script"><span>20. </span>Using sqlite3 in a shell script</h1>
<p>
One way to use sqlite3 in a shell script is to use "echo" or
"cat" to generate a sequence of commands in a file, then invoke sqlite3
while redirecting input from the generated command file. This
works fine and is appropriate in many circumstances. But as
an added convenience, sqlite3 allows a single SQL command to be
entered on the command line as a second argument after the
database name. When the sqlite3 program is launched with two
arguments, the second argument is passed to the SQLite library
for processing, the query results are printed on standard output
in list mode, and the program exits. This mechanism is designed
to make sqlite3 easy to use in conjunction with programs like
"awk". For example:</p>
<div class="codeblock"><pre>$ <b>sqlite3 ex1 'select * from tbl1' |</b>
&gt; <b> awk '{printf "&lt;tr&gt;&lt;td&gt;%s&lt;td&gt;%s\n",$1,$2 }'</b>
&lt;tr&gt;&lt;td&gt;hello&lt;td&gt;10
&lt;tr&gt;&lt;td&gt;goodbye&lt;td&gt;20
$
</pre></div>
<a name="endsh"></a>
<h1 id="ending_shell_commands"><span>21. </span>Ending shell commands</h1>
<p>
SQLite commands are normally terminated by a semicolon. In the shell
you can also use the word "GO" (case-insensitive) or a slash character
"/" on a line by itself to end a command. These are used by SQL Server
and Oracle, respectively. These won't work in <b>sqlite3_exec()</b>,
because the shell translates these into a semicolon before passing them
to that function.</p>
<a name="compiling"></a>
<h1 id="compiling_the_sqlite3_program_from_sources"><span>22. </span>Compiling the sqlite3 program from sources</h1>
<p>
To compile the command-line shell on unix systems and on Windows with MinGW,
the usual configure-make command works:
</p><div class="codeblock"><pre>sh configure; make
</pre></div>
<p>
The configure-make works whether your are building from the canonical sources
from the source tree, or from an amalgamated bundle. There are few
dependencies. When building from canonical sources, a working
<a href="https://www.tcl.tk/man/tcl8.3/UserCmd/tclsh.htm">tclsh</a> is required.
If using an amalgamation bundle, all the preprocessing work normally
done by tclsh will have already been carried out and only normal build
tools are required.
</p><p>
A working <a href="https://zlib.net">zlib compression library</a> is
needed in order for the <a href="cli.html#sqlar">.archive command</a> to operate.
</p><p>
On Windows with MSVC, use nmake with the Makefile.msc:
</p><div class="codeblock"><pre>nmake /f Makefile.msc
</pre></div>
<p>
For correct operation of the <a href="cli.html#sqlar">.archive command</a>, make a copy of the
<a href="https://zlib.net">zlib source code</a> into the compat/zlib subdirectory
of the source tree and compile this way:
</p><div class="codeblock"><pre>nmake /f Makefile.msc USE_ZLIB=1
</pre></div>
<h2 id="_do_it_yourself_builds_"><span>22.1. </span> Do-It-Yourself Builds </h2>
<p>
The source code to the sqlite3 command line interface is in a single
file named "shell.c". The shell.c source file is generated from other
sources, but most of the code for shell.c can be found in
<a href="https://sqlite.org/src/file/src/shell.c.in">src/shell.c.in</a>.
(Regenerate shell.c by typing "make shell.c" from the canonical source tree.)
<a href="howtocompile.html">Compile</a> the shell.c file (together
with the <a href="amalgamation.html">sqlite3 library source code</a>) to generate
the executable. For example:</p>
<div class="codeblock"><pre>gcc -o sqlite3 shell.c sqlite3.c -ldl -lpthread -lz -lm
</pre></div>
<p>
The following additional compile-time options are recommended in order to
provide a full-featured command-line shell:
</p><ul>
<li> <a href="compile.html#threadsafe">-DSQLITE_THREADSAFE=0</a>
</li><li> <a href="compile.html#enable_explain_comments">-DSQLITE_ENABLE_EXPLAIN_COMMENTS</a>
</li><li> <a href="compile.html#have_zlib">-DSQLITE_HAVE_ZLIB</a>
</li><li> <a href="compile.html#introspection_pragmas">-DSQLITE_INTROSPECTION_PRAGMAS</a>
</li><li> <a href="compile.html#enable_unknown_sql_function">-DSQLITE_ENABLE_UNKNOWN_SQL_FUNCTION</a>
</li><li> <a href="compile.html#enable_stmtvtab">-DSQLITE_ENABLE_STMTVTAB</a>
</li><li> <a href="compile.html#enable_dbpage_vtab">-DSQLITE_ENABLE_DBPAGE_VTAB</a>
</li><li> <a href="compile.html#enable_dbstat_vtab">-DSQLITE_ENABLE_DBSTAT_VTAB</a>
</li><li> <a href="compile.html#enable_offset_sql_func">-DSQLITE_ENABLE_OFFSET_SQL_FUNC</a>
</li><li> <a href="compile.html#enable_json1">-DSQLITE_ENABLE_JSON1</a>
</li><li> <a href="compile.html#enable_rtree">-DSQLITE_ENABLE_RTREE</a>
</li><li> <a href="compile.html#enable_fts4">-DSQLITE_ENABLE_FTS4</a>
</li><li> <a href="compile.html#enable_fts5">-DSQLITE_ENABLE_FTS5</a>
</li></ul>
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