weixin_42596520的博客

Business events, business rules and EDRs(1) Stores have employees/managers.Each STORE has many EMPLOYEEs including part-time and full-time.Each EMPLOYEE can be a MANAGER or not.Each STORE has only one MANAGER.Each EMPLOYEE and MANAGER can only work.

存储过程与函数的区别：存储过程是没有返回值的函数函数是有返回值的存储过程创建存储过程delimiter $create procedure procedureName()begin—sql 语句end$delimiter ;查看已有存储过程show procedure status;调用存储过程call p1();删除存储过程drop procedure p6；存储...

https://www.cnblogs.com/zejin2008/p/4643761.html总结如下：after—是在记录操纵之后触发，是先完成数据的增删改，再触发，触发的语句晚于监视的增删改操作，无法影响前面的增删改动作before—是在记录操纵之前触发，是先完成触发，再增删改，触发的语句先于监视的增删改，我们就有机会判断，修改即将发生的操作，如：我们在触发之前需要判断new值和old...

# 13. 按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩select a.*, (select score from sc b where cid=01 and b.sid = sc.sid) as 01_score,(select score from sc b where cid =02 and b.sid = sc.sid) as 02_score,(select sc...