sql触发器停止行中的重复项

创建触发器

CREATE TRIGGER dbo.uniqueUserQuestion ON dbo.submit_AnswerINSTEAD OF INSERTASBEGIN    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 IENDGO