MySQL的经典用法(六)----动态SQL语句
在存储过程中，动态拼接一个字符串,然后执行之.

DROP PROCEDURE IF EXISTS demoSp;   CREATE PROCEDURE demoSp()BEGIN    set @sqlstr=concat("select count(*) from ", "dual");    prepare stmt from @sqlstr;    EXECUTE stmt;             deallocate prepare stmt;    END;