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<a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Determine If An SQL Statement Writes The Database</h2><blockquote><pre>int sqlite3_stmt_readonly(sqlite3_stmt *pStmt);
</pre></blockquote><p>
The sqlite3_stmt_readonly(X) interface returns true (non-zero) if
and only if the <a href="../c3ref/stmt.html">prepared statement</a> X makes no direct changes to
the content of the database file.</p>
<p>Note that <a href="../c3ref/create_function.html">application-defined SQL functions</a> or
<a href="../vtab.html">virtual tables</a> might change the database indirectly as a side effect.
For example, if an application defines a function "eval()" that
calls <a href="../c3ref/exec.html">sqlite3_exec()</a>, then the following SQL statement would
change the database file through side-effects:</p>
<p><blockquote><pre>
SELECT eval('DELETE FROM t1') FROM t2;
</pre></blockquote></p>
<p>But because the <a href="../lang_select.html">SELECT</a> statement does not change the database file
directly, sqlite3_stmt_readonly() would still return true.</p>
<p>Transaction control statements such as <a href="../lang_transaction.html">BEGIN</a>, <a href="../lang_transaction.html">COMMIT</a>, <a href="../lang_transaction.html">ROLLBACK</a>,
<a href="../lang_savepoint.html">SAVEPOINT</a>, and <a href="../lang_savepoint.html">RELEASE</a> cause sqlite3_stmt_readonly() to return true,
since the statements themselves do not actually modify the database but
rather they control the timing of when other statements modify the
database. The <a href="../lang_attach.html">ATTACH</a> and <a href="../lang_detach.html">DETACH</a> statements also cause
sqlite3_stmt_readonly() to return true since, while those statements
change the configuration of a database connection, they do not make
changes to the content of the database files on disk.
</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>
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