MySQL基础----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;