mysql触发器举例

1. 触发器：删除A表的某条数据之后，将A表的某条数据插入到B表
   CREATE TRIGGER delete_trigger
   AFTER DELETE on A  FOR EACH ROW
   BEGIN
   INSERT INTO B(oldCno,oldCname,oldCredit)VALUES(12,old.cname,old.ccredit);
   END;
2. 编程触发器，也可以搭配if使用
   要创建触发器来使班级表中的班内学生数随着学生的添加自动更新，代码如下：
   DELIMITER |
   create trigger tri_stuInsert after insert
   on student for each row
   begin
     declare c int;
     set c = (select stuCount from class where classID=new.classID);
     update class set stuCount = c + 1 where classID = new.classID;
   end|
   DELIMITER ;
   
   
3. mysql函数----触发器搭配if使用（仓库库存）
   CREATE TRIGGER insert_trigger
   after INSERT on c_record FOR EACH ROW
   BEGIN
   IF new.gType="入库"
   THEN
   UPDATE c_goods SET gNumber=gNumber+new.gNumber WHERE gName=new.gName;
   end if;
   IF new.gType="出库"
   THEN 
   UPDATE c_goods SET gNumber=gNumber-new.gNumber WHERE gName=new.gName;
   end IF;
   END;