DML Trigger for Insert or Update to fire conditionally - sql

Question

I'm trying to create a trigger on table MainDataTable that will insert a row to table EPR conditionally.
These are the conditions.
If an insert is made to table MainDataTable and inserts are enabled in table EPRCheck then do the insert into EPR.
If an update is made to table MainDataTable and updates are enabled in table EPRCheck then do the insert into EPR.
What do I need to do to the WHERE clause in the trigger to get this to work, or maybe I need to have two separate triggers for inserts and updates?
This is the EPRCheck table
IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'EPRCheck')
BEGIN
DROP TABLE EPRCheck
END
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE EPRCheck
([TriggerTypeID] [int] NOT NULL,
[TriggerTypeDesc] [varchar](6) NOT NULL,
[IsEnabled] [bit] NOT NULL,
CONSTRAINT [PK_EPRCheck_TriggerTypeID] PRIMARY KEY CLUSTERED
(
[TriggerTypeID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,
ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]
GO
IF NOT EXISTS (SELECT * FROM EPRCheck WHERE TriggerTypeID = 1)
BEGIN
INSERT INTO EPRCheck
VALUES (1, 'Insert', 1)
END
GO
IF NOT EXISTS (SELECT * FROM EPRCheck WHERE TriggerTypeID = 2)
BEGIN
INSERT INTO EPRCheck
VALUES (2, 'Update', 1)
END
GO
IF NOT EXISTS (SELECT * FROM [dbo].[EPRCheck] WHERE TriggerTypeID = 3)
BEGIN
INSERT INTO EPRCheck
VALUES (3, 'Delete', 1)
END
GO
and this is the trigger
IF EXISTS (SELECT 1 FROM sys.triggers WHERE [name] = 'TriggerEPRInsertUpdate')
BEGIN
DROP TRIGGER TriggerEPRInsertUpdate
END
GO
--Trigger Type
--INSERT = 1
--UPDATE = 2
--DELETE = 3
CREATE TRIGGER TriggerEPRInsertUpdate ON MainDataTable
AFTER INSERT, UPDATE
NOT FOR REPLICATION
AS
DECLARE #insertIsEnabled bit, #updateIsEnabled bit
SET #insertIsEnabled = (SELECT IsEnabled FROM EPRCheck WHERE TriggerTypeID = 1)
SET #updateIsEnabled = (SELECT IsEnabled FROM EPRCheck WHERE TriggerTypeID = 2)
IF #insertIsEnabled = 1 OR #updateIsEnabled = 1
BEGIN
DECLARE #triggerTypeID int
IF EXISTS (SELECT 0 FROM inserted)
BEGIN
IF EXISTS (SELECT 0 FROM deleted)
BEGIN
SELECT #triggerTypeID = 2
END
ELSE
BEGIN
SELECT #triggerTypeID = 1
END
END
ELSE
BEGIN
SELECT #triggerTypeID = 3
END
IF (#triggerTypeID = 1 AND #insertIsEnabled = 1) OR (#triggerTypeID = 2 AND #updateIsEnabled = 1)
BEGIN
DECLARE #createDateTime datetime
SET #createDateTime = GETDATE()
SET XACT_ABORT ON;
SET NOCOUNT ON;
BEGIN TRANSACTION
INSERT INTO EPR
SELECT
NEWID() AS DocumentID,
GETDATE() AS CreateDateTime,
NULL AS ProcessDateTime,
#triggerTypeID AS TriggerTypeID,
1 AS MessageStatus
FROM inserted i
LEFT JOIN deleted d ON i.ID = d.ID
WHERE
(#insertIsEnabled = 1 AND NOT EXISTS (SELECT i.Status, i.KeyDate, i.OtherDate, i.KeyCode, i.OtherCode
EXCEPT
SELECT d.Status, d.KeyDate, d.OtherDate, d.KeyCode, d.OtherCode))
OR
(#updateIsEnabled = 1 AND EXISTS (SELECT i.Status, i.KeyDate, i.OtherDate, i.KeyCode, i.OtherCode
EXCEPT
SELECT d.Status, d.KeyDate, d.OtherDate, d.KeyCode, d.OtherCode))
COMMIT TRANSACTION
END
END

Answer 1

Your issue is here:
WHERE (#insertIsEnabled = 1 AND NOT EXISTS (SELECT i.Status, i.KeyDate, i.OtherDate, i.KeyCode, i.OtherCode
EXCEPT
SELECT d.Status, d.KeyDate, d.OtherDate, d.KeyCode, d.OtherCode))
And specifically with the NOT EXISTS. For all inserted events your deleted records will be null, therefore unless your inserted records are all null you'll always have a record returned, therefore the not exist will return false. You can either change EXCEPT to INTERSECT or change to EXISTS - both will mean this works as required:
Example on db<>fiddle
With that being said, I'd still be inclined to slightly rewrite this dealing with your two scenarios separately, and do away with all the IF/ELSE logic at the start too:
CREATE TRIGGER TriggerEPRInsertUpdate ON dbo.MainDataTable
AFTER INSERT, UPDATE
AS
BEGIN
INSERT INTO EPR (DocumentID, CreatedDateTime, TriggerTypeID, MessageStatus)
SELECT DocumentID = NEWID(), CreateDateTime = GETDATE(), TriggerTypeID = epr.TriggerTypeId, MessageStatus = 1
FROM inserted AS i
INNER JOIN EPRCheck AS epr
ON epr.TriggerTypeDesc = 'Insert'
AND epr.IsEnabled = 1
WHERE NOT EXISTS (SELECT 1 FROM Deleted AS d WHERE d.ID = i.ID)
UNION ALL
SELECT DocumentID = NEWID(), CreateDateTime = GETDATE(), TriggerTypeID = epr.TriggerTypeId, MessageStatus = 1
FROM inserted AS i
INNER JOIN deleted AS d
ON i.ID = d.ID
INNER JOIN EPRCheck AS epr
ON epr.TriggerTypeDesc = 'Update'
AND epr.IsEnabled = 1
WHERE NOT EXISTS
( SELECT i.Status, i.KeyDate, i.OtherDate, i.KeyCode, i.OtherCode
INTERSECT
SELECT d.Status, d.KeyDate, d.OtherDate, d.KeyCode, d.OtherCode
);
END
Example on db<>fiddle