Help with sql 200

[combsn]

Hello,
Im new to this whole Sql 2000 and Im having problems with trying to merge tables.
*IE I have 2 tables with matches and its in order like
idnum1 matches idnum2
aaaaaa bbbbbb
bbbbbb aaaaaa
...and so on for 1 table
but i also have another table with a diff set of data that goes the same way with the same over all id number and im trying to integrate the two and take out the duplicates and put a check mark or something of that sort saying that the over all id number matched both in table 1 and in table 2
if u can help me that would be great

[skhanal]

Please explain with data for all tables.