Question

我有一个像这样的mysql查询：

SELECT SUM(bills.Amount) AS AmountExpense, SUM(assets.Amount) as AmountIncome 
FROM bills, assets where bills.UserId = 11 and assets.UserId =11

样本账单表

id  payee  description  UserId          Amount 
1  john   advance          11           15.0         
2  dave   request          2            13.0 
3  er     request          11           12.0

示例资产表

id  payee  description  UserId          Amount 
1  john   advance          11           40.2        
2  dave   request          2            13.0
3  ww     request          11           14.00

我有AmountExpense的问题，多次记录SUM记录。我在Amount Income方面取得了成功。有什么建议吗？

Answer 1

在这些表中的一个或两个表上，每个用户最多可能有一行。执行聚合后，您需要加入它们。另外，请不要使用旧式非ANSI隐式连接：

SELECT AmountExpense, AmountIncome
FROM (  SELECT  UserId, 
                SUM(Amount) AS AmountExpense
        FROM bills
        GROUP BY UserId) AS b
LEFT JOIN ( SELECT  UserId,
                    SUM(Amount) AmountIncome
            FROM assets
            GROUP BY UserId) AS a
    ON b.UserId = a.UserId
WHERE b.UserId = 11

Answer 2

如果您有可能用户可以在任何一个表中，而不能在另一个表中，那么您需要等同于full outer join。 MySQL不支持该语法，但它支持这一点：

select userid, sum(amountexpense) as amountexpense, sum(amountincome) as amountincome
from (select userid, amount as amountexpense, null as amountincome
      from bills
      union all
      select userid, null, amount as amountincome
      from assets
     ) ba
group by userid;

来自2个不同表的SUM 2字段

2 个答案: