网站流量如何突破,网站的付款链接怎么做的,网站设计欣赏心得体会,seo网站服务公司FOR EACH ROW表示每个匹配行的更新或删除.除非查询中有where条件,否则触发器主体不会遍历整个表数据.下面演示了一个工作示例#xff1a;创建样本表#xff1a;drop table if exists tbl_so_q23374151;create table tbl_so_q23374151 ( i int, v varchar(10) );-- set test d…FOR EACH ROW表示每个匹配行的更新或删除.除非查询中有where条件,否则触发器主体不会遍历整个表数据.下面演示了一个工作示例创建样本表drop table if exists tbl_so_q23374151;create table tbl_so_q23374151 ( i int, v varchar(10) );-- set test datainsert into tbl_so_q23374151values (1,one),(2,two ),(3,three),(10,ten),(11,eleven);-- see current data in table**:select * from tbl_so_q23374151;--------------| i | v |--------------| 1 | one || 2 | two || 3 | three || 10 | ten || 11 | eleven |--------------5 rows in set (0.00 sec)用于记录触发器主体中循环计数的样本表-- let us record, loop count of trigger, in a tabledrop table if exists tbl_so_q23374151_rows_affected;create table tbl_so_q23374151_rows_affected( i int );select count(*) as rows_affected from tbl_so_q23374151_rows_affected;---------------| rows_affected |---------------| 0 |---------------定义删除触发器drop trigger if exists trig_bef_del_on_tbl_so_q23374151;delimiter //create trigger trig_bef_del_on_tbl_so_q23374151 before delete on tbl_so_q23374151for each row beginset cnt if(cnt is null, 1, (cnt1));/* for cross checking save loop count */insert into tbl_so_q23374151_rows_affected values ( cnt );end;//delimiter ;现在,测试删除操作delete from tbl_so_q23374151 where i like %1%;-- now let us see what the loop count wasselect cnt as cnt;------| cnt |------| 3 |------现在,检查主表上的触发效果-- now let us see the table dataselect * from tbl_so_q23374151;-------------| i | v |-------------| 2 | two || 3 | three |-------------2 rows in set (0.00 sec)select count(*) as rows_affected from tbl_so_q23374151_rows_affected;---------------| rows_affected |---------------| 3 |---------------1 row in set (0.00 sec)
