AFTER UPDATE trigger gets fired AFTER INSERT - sql server - sql

Question

I have 2 datatriggers, one is supposed to fire after update and the other one after insert. This is how the beginning of the update trigger looks like:
USE [Database]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER TRIGGER [dbo].[UpdateTrigger]
ON [dbo].[Table1]
AFTER UPDATE
AS
BEGIN
(...)
The after insert trigger looks exactly the same, apart from the fact that there's AFTER INSERT instead of AFTER UPDATE. When I update the Table1, only update trigger is fired. However, when I insert, both triggers are fired. Why? How can I solve it?

Answer 1

When trigger fires there are 2 virtual tables: DELETED and INSERTED. When you insert records you have the records only in INSERTED table, however when you update the record you have old records in DELETED table and new ones in the INSERTED tables. So, basically when you do UPDATE, you are doing DELETE and INSERT. You can easily solve that by identifying if there are records in DELETED table. If there are then it was UPDATE, if there is no then it was INSERT.

Answer 2

I was having the same experience as JerryBox where the separate update trigger would fire when the insert trigger fired.
What I wanted was on inserting a new record an insert trigger would insert the datetime stamp when the record was created and insert the username the record was created by. Conversely, if record was updated add/update last modified datetime and last modified by username.
In my case, when a new record was inserted into the table, the insert trigger would fire and add values to fields in the SAME TABLE (i.e. CreatedBy and CreatedDateTime fields). These additions were ‘seen’ by the update trigger as an update to an existing record so ModifiedBy and ModifiedDateTime fields would also be inserted.
In other words, inserting a new record would cause both insert and update triggers to fire.
Reading the comments on the posting by Dmitrij Kultasev, I came up with the following solution:
Combine both INSERT and UPDATE triggers into a single TRIGGER xxx
ON xxx AFTER INSERT, UPDATE ...
Check for old records in the DELETED table
If records exist in DELETED table then update actions are performed
If no records exist in DELETED table then insert actions are
performed
Combining both triggers into a single trigger has outcome that update of records by an AFTER INSERT trigger does not fire the AFTER UPDATE trigger.
USE [Database]
GO
CREATE TABLE [dbo].[Table1](
[id] [int] IDENTITY(1,1) PRIMARY KEY,
[Data] [nvarchar](255) NULL,
[CreatedBy] [nvarchar](255) NULL,
[CreatedDateTime] [datetime] NULL,
[ModifiedBy] [nvarchar](255) NULL,
[ModifiedDateTime] [datetime] NULL)
GO
CREATE TRIGGER [dbo].[UpdateTrigger]
ON [dbo].[Table1]
AFTER INSERT, UPDATE
AS
BEGIN
IF EXISTS (SELECT 1 FROM deleted)
UPDATE [dbo].[Table1]
SET [ModifiedBy] = SYSTEM_USER,
[ModifiedDateTime] = SYSDATETIME()
FROM inserted i
WHERE i.id = [dbo].[Table1].id
ELSE
UPDATE [dbo].[Table1]
SET [CreatedBy] = SYSTEM_USER,
[CreatedDateTime] = SYSDATETIME()
FROM inserted i
WHERE i.id = [dbo].[Table1].id
END
GO
Edits: Formatting, Improved explanation in response to feedback from andronicus