创建用于限制重复条目的触发器 [英] Create Trigger for Restricting Duplicate Entries

问题描述

任务：通过检查AttendanceDate和EmpCode的组合，如果已经标记了特定emp的出勤，则避免用户插入表tblAttendance。



表：tblAttendance

（EmpCode，AttendanceDate，Status）



问题：无法按照Sql server中的上述要求设计触发器

Task: Avoid user from inserting into Table tblAttendance if Attendance of particular emp is already marked, by checking combination of AttendanceDate and EmpCode.

Table: tblAttendance
(EmpCode, AttendanceDate, Status)

Problem: Not able to design the trigger as per above requirement in Sql server

推荐答案

尝试类似

Try like

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

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