Triggers are often used SqlServer syntax AFTER, INSTEAD OF and Detailed

Create a simple flip-flop

TRIGGER trigger_name the CREATE 
 ON table_name 
 [the WITH the ENCRYPTION] 
  the FOR | an AFTER | INSTEAD OF [DELETE, INSERT, UPDATE] 
 AS 
  T-SQL statements 
GO 

trigger position: database> table> I have here is the table name table_name> Trigger 

explanation:
 1, [ WITH eNCRYPTION]: indicates the flip-encryption, encrypted trigger execution method can not be viewed 

when [dELETE, iNSERT, uPDATE] corresponds to when the delete, insert, update, three actions are triggered

When performing insert, insert data acquisition, can select * from inserted to read 
when performing delete, to obtain data before deletion, can be read select * from deleted 
when executing update, to obtain data before the update, available select * from deleted read take, after acquiring the updated data, the read select * from inserted available

2, AFTER: after a successful operation (here after insertion table_a), the trigger operation performed 
e.g.

CREATE TRIGGER T_A
ON table_a
after insert
as 
begin

declare @id int,@name varchar(20)
select @id=id,@name=name from inserted
insert into table_b values(@id,@name)

end

3, INSTEAD OF: The trigger only "fuse" databases, the triggers can be executed to the desired results, needs to be judged by the trigger logic, because the trigger is often accompanied by a lot of judgment branch. 
For example, 
the CREATE TRIGGER T_B 
the ON table_a 
INSTEAD of INSERT 
AS 
the begin 

the IF EXISTS (SELECT * from table_a WHERE name = (SELECT name from inserted The)) 
ROLLBACK TRANSACTION 
the PRINT 'the name already exists in' 

the ELSE 
the INSERT the INTO table_a the VALUES (SELECT * from inserted The) 
the PRINT ' insert success' 

End