sql - 子查询在“NOT IN”中返回 NULL

Question

这是我的查询

select distinct(Challan_No) 
from  Challan_tb 
where Challan_No not in 
  (
    select Challan_No from Invoice_tb where Customer_ID =2 and InvYear=2013
  ) and InvYear=2013 and Customer_ID =2

子查询正在返回NULL，因此外部查询不起作用

请帮忙

Answer 1

如果您不想过多地更改查询的结构，则有一个简单而明显的解决方法：

select distinct(Challan_No) 
from  Challan_tb 
where Challan_No not in 
  (
    select Challan_No from Invoice_tb where Customer_ID =2 and InvYear=2013
    and Challan_No is not null --This line is new
  ) and InvYear=2013 and Customer_ID =2

Answer 2

您可以尝试使用 LEFT JOIN。我认为 Access 会更好地消化这一点。

select distinct(Challan_tb.Challan_No) 
from Challan_tb 
left join Invoice_tb on Invoice_tb.Challan_No = Challan_tb.Challan_No
where Challan_tb.InvYear=2013 and Challan_tb.Customer_ID=2
and Invoice_tb.InvYear is null --or any other Invoice_tb field