If you have a select like this
select a.name, b.name from table_1 a, table_2 b where a.name=b.name
Here i select the field name from both table_1 and table_2, the a and b are an alias for those table names, and i only want the rows where the name in table_1 = name in table_2.
Hope this was what you where asking about, if not ... 🙂