SQL語法整理（六） 觸發器

定義：

由insert、update、delete等事件來觸發某種特定的操作

建立單條執行語句的觸發器

語法：mysql :

create trigger 觸發器 before | after 觸發事件

on 表名 for each row 執行語句

mssql :

create trigger 觸發器名

on tablename 觸發事件

as 執行語句

oracle :

create trigger 觸發器名

觸發事件

on 作用物件

as 執行語句

eg: 

mysql :
create
trigger dept_trig1 before insert
on department for each row
insert
into trigger_time values
(now()
);mssql :
create
trigger dept_trig1
on department
forinsert
asinsert
into trigger_time values
(getdate())
;

語法：create trigger 觸發器名 before|after 觸發事件

on 表名 for each row

begin

執行語句

end注：在執行多條語句時，會以分號結束，為解決問題，delimiter#

eg: 

create
trigger dept_trig2 after
delete
on department for each row
begin
insert
into trigger_time values
('22:36:36');
insert
into trigger_time values
('23:56:56');
end#

eg: show triggers \g;

eg: 

select
*from information_schema.triggers \g;

eg: 

select
*from information_schema.triggers where trigger_name =
'dept_trig1' \g;

eg: 

select
*from sysobjects where xtype=
'tr'

eg: 

exec sp_helptext 'dept_trig1'

eg: 

select
*from user_objects where lower(object_type)
='tgrigger'

eg: 

select
*from user_triggers where trigger_name = upper(
'trg_stu_log'
);

before觸發器 -> 表操作（insert|update|delete） -> after觸發器

注：乙個表在相同觸發事件的相同觸發事件，只能建立乙個觸發器

eg: 

mysql
create
trigger before_insert before insert
on department for each row
insert
into trigger_test values
(null
,'after_insert');
mssql
create
trigger before_insert
on department
forinsert
asinsert
into trigger_time values
('23:10:10');
go;create
trigger after_insert
on department
after
insert
asinsert
into trigger_time values
('23:14:15'
);

eg: 

drop
trigger dept_trig1;

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