mysql - Mysql select查询中无法使用Case语句？

Question

这是我的查询，并按交易类型 C(贷方)和 D(借方)进行分组，

SELECT 
case 
WHEN ACT.TRANSACTIONTYPE='C' THEN SUM(ACT.AMOUNT) END AS CreditBalance,
case 
WHEN ACT.TRANSACTIONTYPE='D' THEN SUM(ACT.AMOUNT) END AS DebitBalance
FROM accounttransaction ACT 
WHERE ACT.TRANSACTIONTYPE IS NOT NULL
GROUP BY ACT.TRANSACTIONTYPE;

下面是我的结果

CreditBalance DebitBalance
16536          NULL
NULL           9673

现在我想减去 A/C 的余额，然后我需要显示为当前余额账户交易表包括账号、交易类型和金额

Answer 1

您只想要所有贷方/借方金额的总计吗？

如果是这样，可能是以下内容:-

SELECT Accountnumber, SUM(CASE WHEN transactiontype = 'C' THEN amount ELSE -1 * amount END) 
FROM accounttransaction
WHERE transactiontype IS NOT NULL
GROUP BY Accountnumber

或者分别给出贷方和借方金额以及总金额

SELECT Accountnumber, 
    SUM(CASE WHEN transactiontype = 'C' THEN amount ELSE 0 END) AS CreditTotal,
    SUM(CASE WHEN transactiontype = 'D' THEN amount ELSE 0 END) AS DebitTotal,
    SUM(CASE WHEN transactiontype = 'C' THEN amount WHEN transactiontype = 'D' THEN -1 * amount ELSE 0 END) AS OverallTotal
FROM accounttransaction
WHERE transactiontype IS NOT NULL
GROUP BY Accountnumber