Sql server 2008 ms sql分组结果查询

我基本上有一个我创建的交易表，记录发票的进出。 我有一面卖旗和买旗

我想要一个简单的sql，它按月计算销售和购买。 问题是，如果我从组中删除事务类型（mybooks\u trans\u class\u id\u fk），它将不起作用，但如果我将其保留在结果中，这并不是我想要的

SQL:

       SELECT 
        DATEPART(Year, mybooks_trans_transaction_datetime) as 'sales_year',
        DATEPART(Month, mybooks_trans_transaction_datetime) as 'sales_month',
        case 
        when cast( mybooks_trans_class_id_fk as nvarchar(100))!='1' then cast(sum(mybooks_trans_gross_amount) as nvarchar(100))
        else '0' 
        end as total_sales,

        case 
        when cast( mybooks_trans_class_id_fk as nvarchar(100))!='2' then cast(sum(mybooks_trans_gross_amount) as nvarchar(100))  
        else '0' 
        end as total_purchases         
        from view_mybooks_transactions_all_details 
        GROUP BY DATEPART(Year, mybooks_trans_transaction_datetime), 
        DATEPART(MM, mybooks_trans_transaction_datetime),mybooks_trans_class_id_fk

2012     11 0   15300.00

2012     12 0   2500.00

2013    1   0   1300.00

2013    1   600.00  0

2013    2   0   2750.00

2013    2   1500.00 0

结果为：

       SELECT 
        DATEPART(Year, mybooks_trans_transaction_datetime) as 'sales_year',
        DATEPART(Month, mybooks_trans_transaction_datetime) as 'sales_month',
        case 
        when cast( mybooks_trans_class_id_fk as nvarchar(100))!='1' then cast(sum(mybooks_trans_gross_amount) as nvarchar(100))
        else '0' 
        end as total_sales,

        case 
        when cast( mybooks_trans_class_id_fk as nvarchar(100))!='2' then cast(sum(mybooks_trans_gross_amount) as nvarchar(100))  
        else '0' 
        end as total_purchases         
        from view_mybooks_transactions_all_details 
        GROUP BY DATEPART(Year, mybooks_trans_transaction_datetime), 
        DATEPART(MM, mybooks_trans_transaction_datetime),mybooks_trans_class_id_fk

2012     11 0   15300.00

2012     12 0   2500.00

2013    1   0   1300.00

2013    1   600.00  0

2013    2   0   2750.00

2013    2   1500.00 0

但是我希望第1个月只在一行中，这样我想要的结果是

2012    11  0   15300.00

2012    12  0   2500.00

2013    1   600.00  1300.00

2013    2   1500.00 2750.00

有什么建议吗？我的sql能力充其量是中等的

这应该有效：（尽量不要改变太多）