MYSQL：如何從三個表返回查詢計算結果？

Question

我有三個表：

Table1: Salary
Fields: ID,Account_Num,Amount

Table2: Other_Income
Fields: ID,Account_Num,Amount

Table3: Expenses
Fields: ID,Account_Num,Amount

從上面的表格中，如何編寫查詢以返回結果，列出這些表格中的所有帳戶，並顯示這些表格中每個帳戶的余額。

結果應顯示Account_num,Salary,Other_Income,Expenses, balance （ balance=Salary.amount+Other_Income.amount-expenses.amount ）

這三個表可能包含一些不同的帳號。

我一直在想這個很久了，嘗試過加入並加入，但仍然做不到。

有人向我展示/引導我嗎？

Answer 1

我對以下查詢有好運。 本質上，我將Salary，Other_Income和Expenses表中的所有交易合並到一個名為Combine的臨時表中，然后使用group by匯總所有交易！

select Account_Num, sum(Amount)
from (
  select Account_Num, Amount from Salary union
  select Account_Num, Amount from Other_Income union
  select Account_Num, -Amount from Expenses
) as Combined
group by Account_Num;

Answer 2

如果每個帳戶都有薪水，以下查詢可能會有所幫助。

select  Account_Num,(total-d.Amount) as final_amount ( select Account_Num, ifnull(a.Amount,0)+ifnull(b.Amount,0) as total from Salary a
   left join Other_Income b on a.Account_Num=b.Account_Num ) c
   join Expenses d on c.Account_Num=d.Account_Num 

Answer 3

    SELECT Sal.`Account_Num`, sal.`Amount` AS Salary, ot_in.`Amount` AS ExtraIncome , exp.`Amount` AS expenses, (sal.`Amount`+ot_in.`Amount`-exp.`Amount`) As Balance FROM Salary AS Sal INNER JOIN Other_income AS ot_in ON Sal.`Account_Num` = ot_in.`Acount_num` INNER JOIN Expenses AS exp ON Sal.`Account_Num` = ex.`Account_Num`   

在這里，您要從這三個表中獲得通用帳號並從每個表中提取對應的金額，然后將表中的三個表連接起來，並使用給定的公式從收入中減去支出來計算剩余余額。我希望這會有所幫助。