mysql 3 group by 和 sum

Question

我的表中有这些数据 (tb_cash_transaction)

我想将 TYPE 列、CURRENCY_ID 列和 AMOUNT 列分组，这样它就会变成如下所示:

**Currency** **Cash IN** **Cash OUT** **Balance**

14             40000        30000        10000        
15             50000        40000        10000 

规则:

1.按货币分组
2.然后求出该货币的现金总和
3.求出该币种的提现总额
4.获取余额(sum cash in - sum cash out)

如何用mysql实现？我尝试使用 group by 但无法获得所需的输出。

提前致谢

Answer 1

SELECT currency_id,
       SUM(CASE
             WHEN TYPE = 'cash_in' THEN amount
           END) AS cash_in,
       SUM(CASE
             WHEN TYPE = 'cash_out' THEN amount
           END) AS cash_out,
       SUM(CASE
             WHEN TYPE = 'cash_in' THEN amount
             ELSE -amount
           END) AS balance
FROM   tb_cash_transaction
WHERE TYPE IN ('cash_in', 'cash_out') /*<--- Where clause probably not needed
                                       but just in case there are other options*/
GROUP  BY currency_id