你有好几排 expenses 每 budgetID ，所以您的联接会产生那么多行。我倾向于怀疑同样的情况也会发生在 income 我也是。
如果你想要一排 budgetID ，则一个选项是预聚合和 left join （或 outer apply ). 假设您想要每个预算的总费用和收入，您可以执行以下操作：

select b.*, e.expenseAmount, i.amountAmount
from budgets b
left join (
    select budgetID_FK, sum(expenseAmount) expenseAmount 
    from expenses 
    group by budgetID_FK
) e on e.budgetID_FK = b.budgetID
left join (
    select budgetID_FK, sum(incomeAmount) incomeAmount 
    from income 
    group by budgetID_FK
) i on i.budgetID_FK = b.budgetID

现在，您将依赖表中的行分组为 budgetID ，因此无法看到这些表的其他列，例如 incomeCategory 或者 expenseCategory （每个值有多个值） budgetID ).

对于budgetid 3，同一用户的开支表中有4个开支（不同的开支ID）为50.00。我想你想要的是相同类别和预算id的总费用，在这种情况下是预算id 3

SELECT 
Budgets.BudgetID, Budgets.BudgetName, Budgets.Username_FK,   
Budgets.BudgetAmount, Budgets.SavePercentage,
Income.IncomeID, Income.IncomeAmount, Income.IncomeCategory,
ex.ExpensesCategory,
ex.Total_ExpensesAmount, 

FROM Budgets 
LEFT JOIN Income ON Budgets.BudgetID = Income.BudgetID_FK
LEFT JOIN (Select BudgetID_FK, ExpensesCategory, SUM(ExpensesAmount) as Total_ExpensesAmount
           FROM Expenses 
           GROUP BY BudgetID_FK, ExpensesCategory) ex ON Budgets.BudgetID = ex.BudgetID_FK
WHERE BudgetName = '2019'