Compare what records are not in a table from different data base

I have two data base named: MEX USA

both containg a t开发者_运维知识库able named: BOM, I would like to compare these two tables to know what records (Column Named IDBOM) are not on USA data base.

Can you publish the Query please?

I assume this is Oracle.

select field1, field2, field3
from tableA
MINUS
select field1, field2, field3
from tableB

will show you rows in tableA that are not in tableB based on these fields.

You can go across a dblink if needed (...from tableB@someLink)