mysql存储过程执行拼接sql字符串

DELIMITER //
CREATE
    PROCEDURE `test`.`add_test`()
    BEGIN
       DECLARE t1 int default date_format(DATE_ADD(NOW(),INTERVAL 1 MONTH),"%Y%m");
       DECLARE t2 int default unix_timestamp(date_format(DATE_ADD(NOW(),INTERVAL 2 MONTH),"%Y-%m-01"));
       declare s1 varchar(32);
       DECLARE _sql VARCHAR(255);

       set s1 = CONCAT('p',t1);
       set _sql = CONCAT("ALTER TABLE test.`lzc_test` ADD PARTITION(PARTITION ",s1," VALUES LESS THAN (",t2,"))");

       ############以下为重点############

       ## 普通变量改为全局变量
       set @test_sql = _sql;
       ## 预处理需要执行的动态SQL，其中stmt是一个变量
       PREPARE stmt1 FROM @test_sql;
       ##执行SQL语句
       EXECUTE stmt1;
       ## 释放掉预处理段
       DEALLOCATE PREPARE stmt1 ;

       ############以上为重点############

    END //
DELIMITER