Alessandro Bonazzi 5c7aa8c1c0 Patch level : 12.0 no-patch
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Aggiunta documentazione di sqlite 3
2020-11-29 00:32:36 +01:00

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<title>Source Of Data In A Query Result</title>
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<a href="intro.html"><h2>SQLite C Interface</h2></a>
<h2>Source Of Data In A Query Result</h2>
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<blockquote><pre>
const char *sqlite3_column_database_name(sqlite3_stmt*,int);
const void *sqlite3_column_database_name16(sqlite3_stmt*,int);
const char *sqlite3_column_table_name(sqlite3_stmt*,int);
const void *sqlite3_column_table_name16(sqlite3_stmt*,int);
const char *sqlite3_column_origin_name(sqlite3_stmt*,int);
const void *sqlite3_column_origin_name16(sqlite3_stmt*,int);
</pre></blockquote>
<p>
These routines provide a means to determine the database, table, and
table column that is the origin of a particular result column in
<a href="../lang_select.html">SELECT</a> statement.
The name of the database or table or column can be returned as
either a UTF-8 or UTF-16 string. The _database_ routines return
the database name, the _table_ routines return the table name, and
the origin_ routines return the column name.
The returned string is valid until the <a href="../c3ref/stmt.html">prepared statement</a> is destroyed
using <a href="../c3ref/finalize.html">sqlite3_finalize()</a> or until the statement is automatically
reprepared by the first call to <a href="../c3ref/step.html">sqlite3_step()</a> for a particular run
or until the same information is requested
again in a different encoding.</p>
<p>The names returned are the original un-aliased names of the
database, table, and column.</p>
<p>The first argument to these interfaces is a <a href="../c3ref/stmt.html">prepared statement</a>.
These functions return information about the Nth result column returned by
the statement, where N is the second function argument.
The left-most column is column 0 for these routines.</p>
<p>If the Nth column returned by the statement is an expression or
subquery and is not a column value, then all of these functions return
NULL. These routines might also return NULL if a memory allocation error
occurs. Otherwise, they return the name of the attached database, table,
or column that query result column was extracted from.</p>
<p>As with all other SQLite APIs, those whose names end with "16" return
UTF-16 encoded strings and the other functions return UTF-8.</p>
<p>These APIs are only available if the library was compiled with the
<a href="../compile.html#enable_column_metadata">SQLITE_ENABLE_COLUMN_METADATA</a> C-preprocessor symbol.</p>
<p>If two or more threads call one or more
<a href="../c3ref/column_database_name.html">column metadata interfaces</a>
for the same <a href="../c3ref/stmt.html">prepared statement</a> and result column
at the same time then the results are undefined.
</p><p>See also lists of
<a href="objlist.html">Objects</a>,
<a href="constlist.html">Constants</a>, and
<a href="funclist.html">Functions</a>.</p>