MySQL存储过程中执行动态SQL语句

mysql>
mysql> delimiter $$
mysql>
mysql> CREATE PROCEDURE set_col_value
    ->        (in_table     VARCHAR(128),
    ->         in_column    VARCHAR(128),
    ->         in_new_value VARCHAR(1000),
    ->         in_where     VARCHAR(4000))
    ->
    -> BEGIN
    ->    DECLARE l_sql VARCHAR(4000);
    ->    SET l_sql=CONCAT_ws(' ',
    ->                'UPDATE',in_table,
    ->                   'SET',in_column,'=',in_new_value,
    ->                ' WHERE',in_where);
    ->    SET @sql=l_sql;
    ->    PREPARE s1 FROM @sql;
    ->    EXECUTE s1;
    ->    DEALLOCATE PREPARE s1;
    -> END$$
Query OK, 0 rows affected (0.00 sec)