SQL Server查询以计算余额

我希望我的SQL查询可以这样运行

我有两张桌子：

键1，日期，输入

键2，日期，输出

到目前为止，我是通过一个

联合体来实现这一点的：

select Date , In , '' as 'out'
from table1

Union ALL

select Date, '' as In, Out
from table2

余额呢

请帮助我
目前，在SQL Server中计算运行总数的最快也是最实用的方法是使用光标

Declare @RunningTotals Table    
    (
    PrimaryKeyCol int not null Primary Key
    , TableName nvarchar(128) not null
    , Total money not null Default ( 0 )
    )

Declare @Values Cursor
Declare @PrimaryKeyCol int  
Declare @TableName nvarchar(128)
Declare @Date datetime
Declare @In money
Declare @Out money
Set @Values = Cursor Fast_Forward For
        Select Key1, 'Table1' As TableName, Date , In , Null as out
        From table1
        Union All
        Select Key2, 'Table2', Date, Null as In, Out
        From Table2     
        Order By Date

Open @Values
Fetch Next From @Values Into @PrimaryKeyCol, @TableName, @In, @Out

Set @Total = 0
While @@Fetch_Status = 0
Begin
    Set @Total = @Total + Coalesce(@In,0) - Coalesce(@Out,0)

    Insert @RunningTotals( PrimaryKeyCol, TableName, Total ) 
    Values( @PrimaryKeyCol, @TableName, @Total )

    Fetch Next From @Values Into @PrimaryKeyCol, @TableName, @In, @Out
End

Close @Values
Deallocate @Values

Select Date, In, Out, RT.Total
From (
        Select Key1 As PrimaryKeyCol, 'Table1' As TableName, Date , In , Null as out
        From table1
        Union All
        Select Key2, 'Table2', Date, Null as In, Out
        From Table2     
        ) As Z
    Join @RunningTotals As RT
        On RT.PrimaryKeyCol = T.PrimaryKeyCol
            And RT.TableName = Z.TableName

样本数据中500的起始余额来自何处？有关各种方法的讨论，请参阅。可能重复的