DROP TRIGGER `backups`;
delimiter //
create trigger backups
before update on articles
for each row
begin
declare time int(1);
select count(id) into time from articles_backups where article_id=new.id;
if time > 5 then
delete from articles_backups where article_id=new.id order by id asc limit 1;
end if;
end;
//
delimiter ;
需求是wordpress 文章修改一次,备份增加一个,数据库最多保留5个