Only inserting a row if it's not already there

Question

I had always used something similar to the following to achieve it:

INSERT INTO TheTable
SELECT
    @primaryKey,
    @value1,
    @value2
WHERE
    NOT EXIST         


        

Answer 1

Firstly, huge shout out to our man @gbn for his contributions to the community. Can't even begin to explain how often I find myself following his advice.

Anyway, enough fanboy-ing.

To add slightly to his answer, perhaps "enhance" it. For those, like me, left feeling unsettled with what to do in the <> 2627 scenario (and no an empty CATCH is not an option). I found this little nugget from technet.

    BEGIN TRY
       INSERT etc
    END TRY
    BEGIN CATCH
        IF ERROR_NUMBER() <> 2627
          BEGIN
                DECLARE @ErrorMessage NVARCHAR(4000);
                DECLARE @ErrorSeverity INT;
                DECLARE @ErrorState INT;

                SELECT @ErrorMessage = ERROR_MESSAGE(),
                @ErrorSeverity = ERROR_SEVERITY(),
                @ErrorState = ERROR_STATE();

                    RAISERROR (
                        @ErrorMessage,
                        @ErrorSeverity,
                        @ErrorState
                    );
          END
    END CATCH