sql跟蹤內部聯接時某人的記錄不足

Question

我有這樣的查詢，但我想知道是否有比下面的嘗試更好的方法？

在CreditBalance中列出所有信用額少於50且在2018年未進行任何交易的成員的信用余額。

SELECT m.CreditBalance
FROM Member m 
INNER JOIN CreditCard cc
ON m.MemberID=cc.MemberID
INNER JOIN CreditDebitTrans cdt
ON cc.CardNo=cdt.CardNo
WHERE (cdt.TransDateTime  != DATEPART(Year,2018) 
AND
m.CreditBalance<50)

Answer 1

這僅對范圍內的事務進行過濾，然后cdt.CardNo為null（因為這是聯接條件）將意味着該范圍內的cdt記錄存在。

SELECT m.memberid, m.CreditBalance
FROM Member m 
INNER JOIN CreditCard cc
ON m.MemberID=cc.MemberID
LEFT OUTER JOIN CreditDebitTrans cdt
ON cc.CardNo=cdt.CardNo and cdt.TransDateTime>='2018-01-01' and cdt.TransDateTime<'2019-01-01'
WHERE cdt.CardNo Is Null and m.CreditBalance<50
group by m.memberid, m.CreditBalance

Answer 2

您還可以做的是在where子句中創建一個子查詢。 但這與您已經做的幾乎相同：

SELECT 
    m.CreditBalance
FROM 
    Member m 
WHERE   
    m.CreditBalance<50
    AND m.MemberID NOT IN (
        SELECT 
            cc.MemberID
        FROM
            CreditCard cc
        INNER JOIN      
            CreditDebitTrans cdt
        WHERE   
            cdt.TransDateTime = DATEPART(Year,2018) 
    )

Answer 3

我喜歡在這種情況下使用EXISTS 。

SELECT m.CreditBalance
FROM Member m
WHERE
    m.CreditBalance < 50
    -- There are no transactions for the member in 2018:
    AND NOT EXISTS (
        SELECT 1
        FROM CreditCard cc
            INNER JOIN CreditDebitTrans cdt ON cdt.CardNo = cc.CardNo
        WHERE cc.MemberID = m.MemberID
            AND cdt.TransDateTime >= '2018-01-01'
            AND cdt.TransDateTime < '2019-01-01'
    );