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If E is zero, then S becomes +a normal prepared statement. If E is 1, then S behaves as if +its SQL text began with "<a href="../lang_explain.html">EXPLAIN</a>". If E is 2, then S behaves as if +its SQL text began with "<a href="../eqp.html">EXPLAIN QUERY PLAN</a>".</p> + +<p>Calling sqlite3_stmt_explain(S,E) might cause S to be reprepared. +SQLite tries to avoid a reprepare, but a reprepare might be necessary +on the first transition into EXPLAIN or EXPLAIN QUERY PLAN mode.</p> + +<p>Because of the potential need to reprepare, a call to +sqlite3_stmt_explain(S,E) will fail with SQLITE_ERROR if S cannot be +reprepared because it was created using <a href="../c3ref/prepare.html">sqlite3_prepare()</a> instead of +the newer <a href="../c3ref/prepare.html">sqlite3_prepare_v2()</a> or <a href="../c3ref/prepare.html">sqlite3_prepare_v3()</a> interfaces and +hence has no saved SQL text with which to reprepare.</p> + +<p>Changing the explain setting for a prepared statement does not change +the original SQL text for the statement. Hence, if the SQL text originally +began with EXPLAIN or EXPLAIN QUERY PLAN, but sqlite3_stmt_explain(S,0) +is called to convert the statement into an ordinary statement, the EXPLAIN +or EXPLAIN QUERY PLAN keywords will still appear in the sqlite3_sql(S) +output, even though the statement now acts like a normal SQL statement.</p> + +<p>This routine returns SQLITE_OK if the explain mode is successfully +changed, or an error code if the explain mode could not be changed. +The explain mode cannot be changed while a statement is active. +Hence, it is good practice to call <a href="../c3ref/reset.html">sqlite3_reset(S)</a> +immediately prior to calling sqlite3_stmt_explain(S,E). +</p><p>See also lists of + <a href="../c3ref/objlist.html">Objects</a>, + <a href="../c3ref/constlist.html">Constants</a>, and + <a href="../c3ref/funclist.html">Functions</a>.</p> + |