Question

I am studying the trigger and I got a question.

I am creating a trigger to change the time complex.

In the data table weeklymeeting

|section_id| meeting type| days| timestart|timeend|class_id|
| 13       | Lecture     |   5 | 01:00:00 |02:00:00|12     |

timestart and timeend are of datatype TIME

I am creating the trigger that checking the time complex

for example

if user uses query like

INSERT INTO DBO.WeeklyMeetings VALUES (35, 1,1 ,'11:40:00','11:42:00', 42)

it should insert the data

however

INSERT INTO CSE132B.DBO.WeeklyMeetings VALUES (35, 1, 1, '12:30:00','01:30:00', 42)

then it must return error message because it is time complex

Therefore I created a trigger to check the time complex..but such as

ALTER TRIGGER [dbo].[check_section_time_complex] ON [dbo].[WeeklyMeetings]
FOR INSERT AS
IF EXISTS(select * from inserted as i INNER JOIN dbo.WeeklyMeetings as m  ON (i.timestart BETWEEN m.timestart and m.timeend)  
OR( i.timeend BETWEEN m.timestart and m.timeend ))
begin
 RAISERROR ('Can not update data because  section time is complexing with other section!!', 16,1);
rollback tran
end

however, it is not really working…i am not really sure that reason….

does anyone knows problems in this trigger ?

thanks

Answer 1

If by “it’s not really working” you mean that it’s allowing conflicting data to be inserted and then raising an error, this is because you’ve specified a FOR INSERT trigger which means that it’s happening after the data is inserted.

If you want to prevent the data being inserted you’ll need to use an INSTEAD OF trigger which happens before insert and within that do the insert yourself if it is valid.

See http://msdn.microsoft.com/en-us/library/ms189799.aspx for the trigger definition.

If the error is something else please describe it more fully.