Question

一旦条件满足，是否可以让SQL停止检查WHERE子句？例如，如果我有如下声明：

SELECT * FROM Table1 
WHERE Table1.SubID = (SELECT TOP 1 SubID FROM Table2 ORDER BY Date DESC) 
OR Table1.OrderID = (SELECT TOP 1 OrderID FROM Table2 ORDER BY Date DESC)

第一次检查后是否可以停止执行？实质上，只应使用where子句中的两个检查中的一个，优先于第一个。以下示例案例。

示例案例：

案例1

Table1 SubID=600 OrderID=5

Table2 TOP 1 SubID=NULL

Table2 TOP 1 OrderID=5

Matches the OrderID to 5

案例2

Table1 SubId=600 OrderId=5

Table2 Top 1 SubID=600

Table2 Top 1 OrderID=3

Matches to SubID=600, not OrderID=3

鉴于建议的答案，with似乎是解决SQL本身无法做到的最佳解决方案。对于我的具体情况，尝试将其置于outer apply时会出现问题，如下所示。

SELECT * FROM tbl_MainFields
OUTER APPLY
(
    WITH conditional AS
    (
        SELECT 1 AS 'choice', PlanCode, Carrier
        FROM tbl_payers
        WHERE tbl_payers.PlanCode = 
            (
                SELECT TOP 1 PlanCode 
                FROM tbl_payerDenials 
                WHERE tbl_payerDenials.AccountNumber = tbl_mainFields.AccountNumber
                ORDER BY InsertDate DESC
            )
        UNION ALL
        SELECT 2 AS 'choice', PlanCode, Carrier
        FROM tbl_payers
        WHERE tbl_payers.OrderNum = 
            (
                SELECT TOP 1 DenialLevel
                FROM tbl_payerDenials
                WHERE tbl_payerDenials.AccountNumber = tbl_mainFields.AccountNumber
                ORDER BY InsertDate DESC
            )
)
SELECT
    PlanCode AS DenialPC,
    Carrier AS DenialCAR
FROM conditional
WHERE choice = (SELECT MIN(choice) FROM conditional)    

) denialData

Answer 1

我认为你可以尝试这样的事情

WITH conditional AS(

    SELECT 1 AS 'choice', PlanCode, Carrier
    FROM tbl_payers
    WHERE tbl_payers.PlanCode = 
        (
            SELECT TOP 1 PlanCode 
            FROM tbl_payerDenials
                JOIN tbl_mainFields ON 
                  tbl_payerDenials.AccountNumber = tbl_mainFields.AccountNumber
            ORDER BY InsertDate DESC
        )

    UNION ALL

    SELECT 2 AS 'choice', PlanCode, Carrier
    FROM tbl_payers
    WHERE tbl_payers.OrderNum = 
        (
            SELECT TOP 1 DenialLevel
            FROM tbl_payerDenials
                JOIN tbl_mainFields ON 
                  tbl_payerDenials.AccountNumber = tbl_mainFields.AccountNumber
            ORDER BY InsertDate DESC
        )
)
SELECT * FROM tbl_MainFields tMF
OUTER APPLY
(    
    SELECT * 
    FROM conditional c
    WHERE c.choice = (SELECT MIN(choice) FROM conditional)
) denialData

我正在使用1和2值来mark查询，然后从第一个中选择信息，如果它返回值，否则返回第二个值查询（MIN(choice)部分）。

我希望很清楚。

Answer 2

不，这不可能。查询优化器在发送查询时会优化整个查询。此外，它还会创建一个计划来利用整个查询。如果你需要这样做，你会想看看这样的事情：

SELECT *
INTO #tbl
FROM Table1
WHERE Table1.SubID = (SELECT TOP 1 SubID FROM Table2 ORDER BY Date DESC)

IF ( NOT EXISTS (SELECT * FROM #tbl) )
BEGIN
    SELECT *
    INTO #tbl
    FROM Table1
    WHERE Table1.OrderID = (SELECT TOP 1 OrderID FROM Table2 ORDER BY Date DESC)
END

Answer 3

归功于@RaduGheorghiu的灵感。此功能类似于建议的WITH和MIN组合，但允许在OUTER APPLY

中使用

SELECT * FROM tbl_MainFields
OUTER APPLY
(
    SELECT TOP 1
        PlanCode AS DenialPC,
        Carrier AS DenialCAR,
        Precedence
    FROM
    (
        SELECT 
            1 AS 'Precedence', 
            PlanCode, 
            Carrier
        FROM tbl_payers
        WHERE tbl_payers.PlanCode = 
            (
                SELECT TOP 1 PlanCode 
                FROM tbl_payerDenials 
                WHERE tbl_payerDenials.AccountNumber = tbl_mainFields.AccountNumber
                ORDER BY InsertDate DESC
            )
        UNION ALL
        SELECT 
            2 AS 'Precedence', 
            PlanCode, 
            Carrier
        FROM tbl_payers
        WHERE tbl_payers.OrderNum = 
            (
                SELECT TOP 1 DenialLevel
                FROM tbl_payerDenials
                WHERE tbl_payerDenials.AccountNumber = tbl_mainFields.AccountNumber
                ORDER BY InsertDate DESC
            )
    ) AS denialPrecedence
    ORDER BY Precedence
) denialData

SQL或首次检查后停止

3 个答案: