mysql - 两个表中两列的总和 - MySQL

Question

我有三张 table

t1
CustId    Name
1         XYZ
2         PQR

t2
CustId    Income
1         100
1         200
2         50
2         100

t3
CustId   Expense
1        50
1        70
2        30
2        40

我需要运行一个查询，得到以下结果

CustId    Total Income     Total Expense
1         300              120
2         150              70

我尝试了正常的 SUM 和 Group By 但结果与预期有很大不同...

我尝试的查询是

SELECT t1.custid, SUM(t2.Income), SUM(t3.Expense) FROM t1
LEFT JOIN t2 ON t1.custId = t2.CustId
LEFT JOIN t3 ON t1.CustId = t3.CustId
GROUP BY t1.CustId

您将不胜感激的任何帮助......

Answer 1

尝试以下查询。

SELECT t1.CustID, IFNULL(tbl1.Income,0) AS 'TotalIncome', IFNULL(tbl2.Expenses,0) AS 'TotalExpenses' 
FROM t1
LEFT JOIN (SELECT t2.CustID,SUM(Income) AS 'Income' FROM t2 GROUP BY t2.CustID) tbl1
ON t1.CustID = tbl1.CustID
LEFT JOIN (SELECT t3.CustID,SUM(Expenses) AS 'Expenses' FROM t3 GROUP BY t3.CustID) tbl2
ON t1.CustID = tbl2.CustID;

SQL fiddle :http://sqlfiddle.com/#!9/ad05d/8