MS SQL common SQL statements (6): create, modify, delete triggers and other operations sq

6. Trigger operation:

--1. Create a trigger
create trigger tesetTrigger -- trigger name
on employee -- on which table the trigger is defined
for insert -- trigger type
as -- program statement
begin
	print 'tesetTrigger is used';
end

--2, call
insert into employee(empName,empAge,empPay,empJob)
values('Mr. Li',25,2500,'Senior Lecturer')


--3. Specify the trigger sequence of the trigger: only the first and last one can be specified, and the random trigger in the middle
--Create 6 insert triggers first
declare @count int;
declare @c int;
declare @triggerName varchar(50);
declare @sql varchar(100);
declare @msg varchar(50);
set @count = 6;
set @c = 1;
while(@c<=@count)
begin
	set @triggerName = 'tesetTrigger'+cast(@c as varchar(5));
	set @msg = @triggerName+'trigger was called';
	set @sql='create trigger '+@triggerName+' on employee for insert as begin print '''+@msg+''' end ';
	set @sql='create trigger '+@triggerName+' on employee for insert as begin print '''+@msg+''' end ';
	print @sql;
	exec(@sql);
	set @c = @c+1;
end

--Execute the insert statement to view the calling sequence: tesetTrigger1, tesetTrigger2, tesetTrigger3, tesetTrigger4, tesetTrigger5, tesetTrigger6 triggers are called in sequence
insert into employee(empName,empAge,empPay,empJob)
values('Teacher He',35,7500,'Senior Lecturer');

--Adjust the execution process of the trigger: only the first and last ones can be adjusted, the first one is defined as tesetTrigger6, and the last one is defined as tesetTrigger1
exec sp_settriggerorder @triggername='tesetTrigger6',@order='first',@stmttype='insert';
exec sp_settriggerorder @triggername='tesetTrigger1',@order='last',@stmttype='insert';

--Execute sql to view the sequence: tesetTrigger6, tesetTrigger2, tesetTrigger3, tesetTrigger4, tesetTrigger5, tesetTrigger1 triggers are called in sequence
insert into employee(empName,empAge,empPay,empJob)
values('Mr. Xiaolan',20,3500,'Assistant');

--Cancel the execution order specified by the trigger
exec sp_settriggerorder @triggername='tesetTrigger6',@order='none',@stmttype='insert';
exec sp_settriggerorder @triggername='tesetTrigger1',@order='none',@stmttype='insert';

--Execute the insert statement to view the calling sequence: tesetTrigger1, tesetTrigger2, tesetTrigger3, tesetTrigger4, tesetTrigger5, tesetTrigger6 triggers are called in sequence
insert into employee(empName,empAge,empPay,empJob)
values('Mr. Xiaojin',24,3500,'Assistant');

--sp_settriggerorder trigger structure:
exec sp_settriggerorder @triggername='trigger name',@order='first|last|none',@stmttype='trigger type, insert|update|delete optional';

--4, instead of triggers
--Create a for delete trigger first
create trigger tesetDeleteTrigger
on employee
for delete
as
begin
	print 'tesetDeleteTrigger was called';
end

--Execute the delete operation to view the execution: data is deleted and the console prints "tesetDeleteTrigger trigger was called"
delete from employee where empId=15;

--Create another delete trigger instead of
create trigger tesetInsteadOfDeleteTrigger
on employee
instead of delete
as
begin
	print 'The alternative trigger tesetInsteadOfDeleteTrigger was called';
end

--Execute the delete operation to view the execution: the console prints "the alternative trigger tesetInsteadOfDeleteTrigger was called" but the data is not deleted
delete from employee where empId=16;

--Compare:
--for trigger: directly manipulate data, such as adding, deleting data, etc., the data in the database changes after execution
--instead of trigger: do not operate the data, just perform the "operation specified in the trigger", and the data does not change

--5, view the trigger
SELECT name, definition
FROM sys.sql_modules AS m
INNER JOIN sys.all_objects AS o ON m.object_id = o.object_id
WHERE o.[type] = 'tr'

--6, modify the trigger
--The modification is consistent with the creation syntax structure, that is, the created keyword can be modified to the alter keyword. As for the business logic, it can be modified according to the actual situation.
ALTER trigger tesetDeleteTrigger
on employee
for insert,update,delete
as
begin
	print 'The tesetDeleteTrigger trigger was called after modification';
end

--7, delete trigger
drop trigger tesetDeleteTrigger;


--8. View the basic information of the trigger, including name, owner, type and creation time
exec sp_help tesetDeleteTrigger;

--9. View the trigger creation code
exec sp_helptext tesetDeleteTrigger;
--Note: If all the code when creating a new trigger is one line (such as tesetTrigger1), then the found code is one line. If the format is set such as tesetDeleteTrigger, then the code is displayed line by line as it is newly created.