sql查询查找源中存在的值

Question

我有以下查询，

select Vendor_ID, Descr, source, Name, Parent_Vendor_ID from VENDOR; 

数据：

VendorID       Descr    Source  name     Parent Vendor ID
1234          ONLINE    ABC     JACK     6666
5689          OFFSHORE  XYZ      SAM     5555
9999          SHOP      TTT     EBAY     1234
6666         ECOMMERCE  FRE    AMERICAS 

从上表中，数据5555不存在于供应商ID字段中。所以我需要输出如下

VendorID    Descr      Source   name    Parent Vendor ID    EXIST
1234        ONLINE      ABC     JACK    6666                Yes
5689        OFFSHORE    XYZ     SAM    **5555               No**
9999        SHOP        TTT     EBAY    1234                Yes
6666        ECOMMERCE   FRE    AMERICAS     

我需要查找字段1 Vendor_ID中是否存在Parent_Vendor_ID。如果存在则只需要一个带有是/否的列。如果是，则否则否

输出应为所有字段+ Parent_Vendor_ID_Exist

select Vendor_ID, Descr, source, Name, Parent_Vendor_ID,Parent_Vendor_ID Exist

我尝试了，否则它没有返回所有值。有人可以建议吗？

Answer 1

select v1.Vendor_ID, v1.Descr, v1.source, v1.Name, v1.Parent_Vendor_ID,
       case when v2.Vendor_ID is null 
            then 'NO'
            else 'YES' 
       end as Parent_Vendor_ID_Exist
from vendor v1
left join vendor v2 on v1.Parent_Vendor_ID = v2.Vendor_ID

Answer 2

SELECT v1.Vendor_ID
     , v1.Descr
     , v1.source
     , v1.Name
     , v1.Parent_Vendor_ID
     , nvl2(v2.vendor_id,'Yes','No') as parent_exist
  FROM VENDOR v1 
  LEFT OUTER JOIN vendor v2 
      ON (v1.parent_vandor_id = v2.vendor_id); 

Answer 3

试试这个..

SELECT Vendor_ID, Descr, source, Name, Parent_Vendor_ID,
CASE  
     WHEN 
         EXISTS( SELECT Vendor_ID FROM VENDOR v2 WHERE v1.Parent_Vendor_ID = v2.Vendor_ID)
    THEN
        'Yes'
    ELSE
        'No'
    END as "Parent_Vendor_ID Exist"
 FROM VENDOR v1; 

让我知道这是否有效。