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table comparison in Acccess

Posted on 2011-02-10
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Last Modified: 2012-05-11
I have 2 tables (A and B) with the same structure, what is the easiest way to obtain a list of combined record without double counting the row with the same record in a chosen field?
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Question by:fitaliano
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5 Comments
 
LVL 31

Expert Comment

by:Helen Feddema
ID: 34864459
A union query should do it:


SELECT *
FROM tblContacts
UNION SELECT * FROM tblMoreContacts;

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Author Comment

by:fitaliano
ID: 34864510
How do I ensure that Last Names are not double-counted?
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LVL 77

Expert Comment

by:peter57r
ID: 34864825
Union will eliminate duplicates but the duplication is based on all selected fields.
If you want to base duplication just on one field then you will have to come up with some rules about how you decide which record to keep and which to remove.  You will probably then need a second process to get the final list.
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Author Comment

by:fitaliano
ID: 34864913
Thanks Peter,

can you be more specific?

This is exactly what I would like to do:

I have [Address] and [Last Name] in both table A and B.

I want to obtain a list that combines both tables where the same [Last Name] in A and B is counted only once.  If there is a match between [Last Name] I want table A to win


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LVL 77

Accepted Solution

by:
peter57r earned 500 total points
ID: 34870324
In that case use your equivalent of...

Select * from tableA
Union
Select * from TableB as B where  not exists (Select Lastname from tableA where TableA.Lastname = B.Lastname)
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