Combining NOT EXISTS with INSERT ... SELECT - sql-server

Question

The following code inserts a new row into a table based on a value in another row but it also allows duplicate data. I want to use NOT EXISTS so that if there is already a row with that value then it won't insert another one, but not sure how to integrate this.
INSERT INTO [Grading].[dbo].[tblObservations]
([FormID]
,[Data]
,[UserID]
,[DateOfObservation]
,[Final]
,[ValidTo]
,[ID_Grading]
,[ID_ObservationKind]
,[Created]
,[Modified]
,[RowVersion])
SELECT [FormID]
,'0'
,[UserID]
,[DateOfObservation]
,[Final]
,[ValidTo]
,[ID_Grading]
,40
,[Created]
,[Modified]
,[RowVersion]
FROM [Grading].[dbo].[tblObservations]
WHERE [ID_ObservationKind] = 39 AND [Data] = 'No' AND [Final] = 1
Any help appreciated.

Answer 1

Try this one -
USE [Grading]
INSERT INTO [dbo].[tblObservations]
(
FormID
, Data
, UserID
, DateOfObservation
, Final
, ValidTo
, ID_Grading
, ID_ObservationKind
, Created
, Modified
, [RowVersion]
)
SELECT
t.FormID
, '0'
, t.UserID
, t.DateOfObservation
, t.Final
, t.ValidTo
, t.ID_Grading
, 40
, t.Created
, t.Modified
, t.[RowVersion]
FROM dbo.tblObservations t
LEFT JOIN dbo.tblObservations t2 ON
t.FormID = t2.FormID
AND t2.Data = '0'
AND t.UserID = t2.UserID
AND t.DateOfObservation = t2.DateOfObservation
AND t.Final = t2.Final
AND t.ValidTo = t2.ValidTo
AND t.ID_Grading = t2.ID_Grading
AND t2.ID_ObservationKind = 40
AND t.Created = t2.Created
AND t.Modified = t2.Modified
AND t.[RowVersion] = t2.[RowVersion]
WHERE t.ID_ObservationKind = 39
AND t.Data = 'No'
AND t.Final = 1
AND t2.FormID IS NULL
Or try this -
INSERT INTO [dbo].[tblObservations]
(
FormID
, Data
, UserID
, DateOfObservation
, Final
, ValidTo
, ID_Grading
, ID_ObservationKind
, Created
, Modified
, [RowVersion]
)
SELECT
t.FormID
, '0'
, t.UserID
, t.DateOfObservation
, t.Final
, t.ValidTo
, t.ID_Grading
, 40
, t.Created
, t.Modified
, t.[RowVersion]
FROM dbo.tblObservations t
WHERE t.ID_ObservationKind = 39
AND t.Data = 'No'
AND t.Final = 1
AND NOT EXISTS(
SELECT 1
FROM dbo.tblObservations t2
WHERE t2.ID_ObservationKind = 39
AND t2.Data = 'No'
AND t2.Final = 1
)

Answer 2

You can try
IF NOT EXISTS
(
SELECT 1
FROM [Grading].[dbo].[tblObservations]
WHERE [ID_ObservationKind] = 39 AND [Data] = 'No' AND [Final] = 1
)
BEGIN
-- Insert script
END

Answer 3

You're looking to do a "merge" or "upsert" in SQL. Depending on your database, there are a number of ways to do this. If you are using MySQL, you'll want to use it's INSERT... ON DUPLICATE KEY UPDATE syntax.