在sql中选择空值

Question

我有两张桌子

1. xx_new.xx_online_registrations@appsread.prd.com oreg
2. m_warranty_sku MSK

在oreg表中，对于字段ora_warranty_id，我有一些空值，但是在MSK表中，我没有空值，所以当我加入这两个表时，oreg的空值列被过滤了，我是否也可以捕获这些数据。我在下面做qry，但不确定这是否正确。

select *
from
    (
    select 
   oreg.ora_warranty_id,
   mdh.warranty_sku_num
    from
     mdhdba.m_warranty_sku mdh
         , xx_new.xx_online_registrations@appsread.prd.com oreg
    where
   mdh.warranty_sku_num= oreg.ora_warranty_id(+) -----ora_warranty_id from  xx_new.xx_online_registration table
   )
where ora_warranty_id is  null -- oreg.ora_warranty_id

Answer 1

希望这能帮上忙

    select *
from
    (
    select 
   oreg.ora_warranty_id,
   mdh.warranty_sku_num
    from
     mdhdba.m_warranty_sku mdh
         , xx_new.xx_online_registrations@appsread.prd.com oreg
    where
   oreg.ora_warranty_id = mdh.warranty_sku_num(+) -----ora_warranty_id from  xx_new.xx_online_registration table
   )
where ora_warranty_id is  null -- oreg.ora_warranty_id