使用带有SQL联合的过滤器

Question

我有这个SQL Server查询。执行此查询将给出claimnumbers列表和UW_Peril。

SQL Server：

select 
    ClaimNum, UW_Peril  
from 
    tableA

union

select  
    ClaimNum, UW_Peril 
from 
    (select 
         claimNum, 'Litigation' as UW_Peril 
     from 
         tableB
     where 
         Litigation = 1 and OrderofSuitReceived = 1) lt

我有2个案例：

1. 如果每个索赔号只有一行，则保持原样。
2. 但如果每个索赔号超过行数，则选择UW_Peril =＆＃39;诉讼＆＃39;

示例：

ClaimNum    UW_Peril
--------------------------
2053057     Litigation
2053057     Theft
2053125     Litigation
2052452     Subro

预期输出

示例：

ClaimNum    UW_Peril
--------------------------
2053057     Litigation
2053125     Litigation
2052452     Subro

我该如何修改？提前致谢

Answer 1

您可以将exists和not exists与union all：

一起使用

select ClaimNum, UW_Peril
from tableB b
where exists (select 1 
              from tableB b1 
              where b1.ClaimNum = b.ClaimNum and b1.UW_Peril = b.UW_Peril)
union all
select ClaimNum, UW_Peril
from tableB b
where not exists (select 1 
                  from tableB b1 
                  where b1.ClaimNum = b.ClaimNum and b1.UW_Peril = b.UW_Peril) and
      b.UW_Peril = 'Lititgation';