As mentioned earlier, it is more efficient to reuse statements than to drop them and allocate new ones. Before executing a new SQL statement on a statement, applications should be sure that the current statement settings are appropriate. These include statement attributes, parameter bindings, and result set bindings. Generally, parameters and result sets for the old SQL statement need to be unbound (by calling SQLFreeStmt with the SQL_RESET_PARAMS and SQL_UNBIND options) and rebound for the new SQL statement.
When the application has finished using the statement, it calls SQLFreeHandle to free the statement. After freeing the statement, it is an application programming error to use the statement's handle in a call to an ODBC function; doing so has undefined but probably fatal consequences.
When SQLFreeHandle is called, the driver releases the structure used to store information about the statement.
SQLDisconnect automatically frees all statements on a connection.