Sql server sql server结果的两倍和三倍

我想创建一个特定的表，但是一些数值在结果中是两倍或三倍的。 情况如下：

表2：付款和费用

[Payments]: ID, studentID, Amount, DOP (a row in this table is a payment which a student pays it on DOP (date).
[Expenses]: ID, AmountPaid, TimeStamp (a row in this table is an expense bought such as papers or pens... on a specific date(timestamp)

我的问题是：

select
sum(purchases.amount) as 'Income From Students',
sum(Expenses.amountpaid) as 'Expenses',
sum(purchases.amount-expenses.amountpaid) as 'Net Profit',
datename(month,timestamp) as 'Month',
datepart(year,timestamp) as 'Year' 
from expenses,purchases 
group by datename(month,timestamp),datepart(year,timestamp)

select sum(P.Income) as 'Income from Payments',
sum(E.expense) as 'Expenses',
sum(P.Income)-sum(E.expense) as 'Net Profit',
DateName( month , DateAdd( month , IncomeMonth , 0 ) - 1 ) as 'Month'
from
(select sum(payments.amountpaid) as Income,
month(DOP) as IncomeMonth
from payments group by month(dop)) as P,
(select sum(expenses.amountpaid) as Expense,
month(timestamp) as ExpenseMonth
from expenses 
group by month(timestamp))
as E
where
E.Expensemonth=P.IncomeMonth
group by P.IncomeMonth

如查询所示：我的表格应显示每月和每年的付款、费用和净

利润=付款-费用之和

问题是，当得到结果时，总金额（费用。支付金额）总是加倍

因此，任何想法…
听起来都需要指定两个表之间的关系

我想是这样的：

select
sum(purchases.amount) as 'Income From Students',
sum(Expenses.amountpaid) as 'Expenses',
sum(purchases.amount-expenses.amountpaid) as 'Net Profit',
datename(month,timestamp) as 'Month',
datepart(year,timestamp) as 'Year' 
from expenses,purchases 
WHERE PURCHASES.DOP = EXPENSES.TIMESTAMP /*Add this*/
group by datename(month,timestamp),datepart(year,timestamp)

我解决了，伙计们，经过4个小时的尝试，问题是：

select
sum(purchases.amount) as 'Income From Students',
sum(Expenses.amountpaid) as 'Expenses',
sum(purchases.amount-expenses.amountpaid) as 'Net Profit',
datename(month,timestamp) as 'Month',
datepart(year,timestamp) as 'Year' 
from expenses,purchases 
group by datename(month,timestamp),datepart(year,timestamp)

select sum(P.Income) as 'Income from Payments',
sum(E.expense) as 'Expenses',
sum(P.Income)-sum(E.expense) as 'Net Profit',
DateName( month , DateAdd( month , IncomeMonth , 0 ) - 1 ) as 'Month'
from
(select sum(payments.amountpaid) as Income,
month(DOP) as IncomeMonth
from payments group by month(dop)) as P,
(select sum(expenses.amountpaid) as Expense,
month(timestamp) as ExpenseMonth
from expenses 
group by month(timestamp))
as E
where
E.Expensemonth=P.IncomeMonth
group by P.IncomeMonth

表之间没有关系吗？e、 g.假设两行费用（2012年1月）（2012年2月）加上4行付款将产生8行视图（从费用、采购）它们之间没有关系如果Nick不对（我认为他应该是对的），那么在不改变设计的情况下，您的问题就没有解决方案。@AliMkahal如果您的问题得到解决，然后别忘了接受有用的答案。这没有关系，只是我需要计算每个月内的所有采购和费用，然后从每个月获得（采购费用）。虽然有关系。。。月份和年份。必须将每个月的购买与每个月的支出分别关联起来-否则，您无法按月正确地分解数据。如果您没有从该查询中返回任何内容，可能是因为您的DOP和Timestamp列不完全匹配（甚至到毫秒），因此，您可以将日期设置为月份，也可以使用：WHERE YEAR（DOP）=YEAR（Timestamp）和month（DOP）=month（Timestamp）列“T.Income”在选择列表中无效，因为它既不包含在聚合函数中，也不包含在GROUP BY子句中。其中P.ID=E.ID是不必要的，因为不需要在两者之间建立关系tables@AliMkahal
其中P.ID=E.ID不是不必要的
dude，这是获得双精度值的唯一原因。如果不使用它，它将添加冗余值。明白了吗？没有关系，也不需要关系。我会尽量多解释的。假设表“付款”有：-记录：100$11-10-2012-记录：150$12-10-2012-记录：140$12-11-2012-记录：120$10-12-2012，因此，我们这里的总数为，第10个月250$11个月140$12个月120$12个月。同样的概念也适用于费用，然后我希望结果表显示一个月的列表，以及每个月下一个月的总费用。正如你所总结的，没有必要建立关系。