mysql触发器 实例_mysql触发器的三个例子
本節內容：
mysql觸發器實例
例1，
復制代碼 代碼示例:
delimiter //
create trigger InsertUser
before insert on user
for each row
Begin
insert into user_group(uid,gid) values(new.uid,'group4444444444');
end;//
delimiter ;
例2，
復制代碼 代碼示例:
delimiter //
create trigger InsertUser
before insert on user
for each row
Begin
IF new.Type=2 then
insert into user_group(uid,gid) values(new.uid,'group4444444444');
else
insert into user_group(uid,gid) values(new.uid,'group55555555555')
END IF;
end;//
delimiter ;
例3，
復制代碼 代碼示例:
delimiter //
create trigger InsertUser
before insert on user
for each row
Begin
IF new.type=1 then
insert into user_group(uid,gid) values(new.uid,'578d3369633b47bd9c1fe8bf905cbfb1');
END IF;
IF new.type=2 then
insert into user_group(uid,gid) values(new.uid,'387bcd57fc5a4c3c9de83ee210fef661');
END IF;
end;//
delimiter ;
mySql觸發器實例
在mysql中，使用觸發器能進行一些約束。
例子，當Student表的StudentID列被發生更改時,BorrowStudent表的StudentID列也跟著更改.如果Student表刪除某記錄,BorrowStudent也刪除對應StudentID的記錄.
復制代碼 代碼示例:
/*先刪除將要創建而存在的表*/
drop table if exists Student;
drop table if exists BorrowStudent;
/*創建表*/
create table Student(
StudentID int not null primary key,
StudentName varchar(30) not null,
StudentSex enum('m','f') default 'm'
)engine=myisam;
create table BorrowStudent(
BorrowRecord int not null auto_increment primary key,
StudentID int not null,
BorrorDate date,
ReturnDate date,
foreign key(StudentID) references Student(StudentID)
)engine=myisam;
/*插入記錄*/
insert into Student values(1235412,'java','m');
insert into Student values(3214562,'jiajia','m');
insert into Student values(5441253,'purana','f');
insert into BorrowStudent(StudentID,BorrorDate,ReturnDate)
values(1235412,'2007-01-01','2007-01-07');
insert into BorrowStudent(StudentID,BorrorDate,ReturnDate)
values(3214562,'2007-01-01','2007-01-07');
insert into BorrowStudent(StudentID,BorrorDate,ReturnDate)
values(5441253,'2007-01-01','2007-01-07');
/*創建觸發器*/
delimiter $$
drop trigger if exists tduStudent$$
drop trigger if exists tddStudent$$
create trigger tduStudent before update
on Student for each row
begin
if new.StudentID!=old.StudentID then
update BorrowStudent
set BorrowStudent.StudentID=new.StudentID
where BorrowStudent.StudentID=old.StudentID;
end if;
end$$
create trigger tddStudent before delete
on Student for each row
begin
delete
from BorrowStudent
where BorrowStudent.StudentID=old.StudentID;
end$$
delimiter ;
總結
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