SQL连接,比较两个列值,匹配col值

Question

我有两张桌子.

Table 1 columns are
====================
(MAINID,  XID, Name)
====================
(A1   1  SAP)
(B2   2  BAPS)
(C3   3  SWAMI)

Table 2 columns are
===================
(ID  COL1)
=================== 
(1   XYZ)
(2   ABC)

现在,我想找到Table2的ID列中没有的XID值.在表1中,XID是唯一的,并且在表2中,ID是PK.

Answer 1

select xid 
from table1
where xid not in
(select id from table2)