Question

我一直在尝试创建此函数时遇到无法将数据返回给客户端的错误，我只想通过查询表然后检查@@来了解如何执行以下操作。 ROWCOUNT并根据结果设置位值，如何在不过于复杂的情况下执行此操作？

RETURNS BIT
AS
BEGIN
    -- Set @sDup to False
    DECLARE @sDup BIT = 0   

    --check allDataTemp
    SELECT * FROM tbl1 JOIN ON tbl8 WHERE fld1 = @val1 and fld2 = @val2 
                and fld3 = @val4

    IF (@@ROWCOUNT > 0) 
        BEGIN
            SET @sDup = 1
            RETURN @sDup
        END 

    --check allDataTemp2
    SELECT * FROM tbl2 

    IF (@@ROWCOUNT > 0)
        BEGIN
            SET @sDup = 1
            RETURN @sDup
        END

    SELECT * FROM tbl3 

    IF (@@ROWCOUNT > 0) 
        BEGIN
            SET @sDup = 1
            RETURN @sDup
        END

    -- Return the result of the function
    RETURN @sDup

Answer 1

问题是你正在尝试选择数据，当它只期望返回BIT值时，它试图输出该选择的结果。请重新尝试使用您的查询：

RETURNS BIT
AS
BEGIN
    -- Set @sDup to False
    DECLARE @sDup BIT = 0   

    --check allDataTemp
    IF (SELECT COUNT(*) FROM tbl1) > 0
        BEGIN
            SET @sDup = 1
            RETURN @sDup
        END 

    --check allDataTemp2
    IF (SELECT COUNT(*) FROM tbl2) > 0
        BEGIN
            SET @sDup = 1
            RETURN @sDup
        END

    IF (SELECT COUNT(*) FROM tbl3) > 0
        BEGIN
            SET @sDup = 1
            RETURN @sDup
        END

    -- Return the result of the function
    RETURN @sDup
END

上面稍微更简洁的版本保持相同的短路逻辑，如下所示：

BEGIN
    -- Set @sDup to False
    DECLARE @sDup BIT = 0

    -- Collect Data and perform logic
    SET @sDup = (CASE
        WHEN (SELECT COUNT(*) FROM tbl1) > 0 THEN 1
        WHEN (SELECT COUNT(*) FROM tbl2) > 0 THEN 1
        WHEN (SELECT COUNT(*) FROM tbl3) > 0 THEN 1
        ELSE 0 END)

    --Return Value
    RETURN @sDup
END

Answer 2

RETURNS BIT
AS
BEGIN
    -- Set @sDup to False
    DECLARE @sDup BIT = 0   

    --check allDataTemp


    IF EXISTS (SELECT * FROM tbl1)
        BEGIN
            SET @sDup = 1
            RETURN @sDup
        END 

    --check allDataTemp2 

    IF EXISTS (SELECT * FROM tbl2)
        BEGIN
            SET @sDup = 1
            RETURN @sDup
        END



    IF EXISTS (SELECT * FROM tbl3)
        BEGIN
            SET @sDup = 1
            RETURN @sDup
        END

    -- Return the result of the function
    RETURN @sDup

由于您只检查是否存在任何行，因此使用带有EXISTS的{{1}}将为您提供最佳性能，因为它将停止执行并在第一次命中后立即返回True，< / p>

Answer 3

您为每个表创建一个计数，设置每个总计的变量，然后只检查一个变量是否为0或者大于0然后返回1

Select语句无法将数据返回给客户端

3 个答案: