Question

I have a table with multiple records:

• User_Name ( e.g. ‘TOM’)
• Question_ID (eg ‘q002’)
• Answer (e.g. ‘D’)

i want to create a trigger so that no one can submit an answer to the same question twice.
It has to be a trigger only.

CREATE TRIGGER trigger_Check_Duplicates

ON submit_Answer

FOR INSERT
AS

IF SELECT???

PRINT 'duplicate'

raiserror('cant submit answer to same question twice')

ROLLBACK

End

Answer 1

Create trigger

CREATE TRIGGER dbo.uniqueUserQuestion 
ON dbo.submit_Answer
INSTEAD OF INSERT
AS
BEGIN
    SET NOCOUNT ON
    IF EXISTS 
    (
        SELECT 1 
        FROM dbo.submit_Answer T 
        INNER JOIN INSERTED I 
        ON T.user_name = I.user_name 
            AND T.question_id = I.question_id
    )
    BEGIN
        -- Do dupe handling here
        PRINT 'duplicate'
        raiserror('cant submit answer to same question twice')
        return
    END

    -- actually add it in
    INSERT INTO
        dbo.submit_Answer
    SELECT
        *
    FROM
        INSERTED I
END
GO