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7/28/2008 3:21:03 PM
Access Tip: Duplicate Records in Two Tables
By Richard Rost   Richard Rost on Facebook Richard Rost on Twitter Richard Rost on Google Plus Richard Rost on LinkedIn Email Richard Rost

Q: I have two tables with customer information. I need to keep the two tables separate, but I would like to delete the duplicates from one of the tables (i.e. delete the customers from table A who are also in table B)?

A: There's really no easy way to take two tables and delete the duplicate records between them. There is a FIND DUPLICATES query, but that only searches for duplicate RECORDS in a single table... which you could do, if you could merge both tables together and then delete all of the duplicates.

Here's my cheap workaround for finding duplicate records between two tables. This assumes you have a field in them (such as CustomerID) that is the same for both tables.

Step 1: add a field in the table that has the records you want to delete called DeleteMe - or something to that effect.

Step 2: JOIN these two tables together in a query by whatever field is related so that when you run the query you see only records that are in both.

Step 3: convert this query over into an UPDATE query. Now, update the value of the DeleteMe field to YES. See this tutorial for help on Update queries:


Step 4: run the query. Now every record that is in BOTH tables (since they're joined) will be marked YES for DeleteMe.

Step 5. Make a new query based on just the table with records that need to be deleted, and set the criteria so DeleteMe = TRUE.

Step 6. Convert this query over to a DELETE query. This should delete only those records.

If you need more help with ACTION QUERIES (make table, delete, update, append, etc.) I cover them in exquisite detail in my Access 222 Tutorial:


Hope this answers your question.

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Keywords: access tips update query delete action
Post Reply

duplicates Comment from Richard Rost @ 7/29/2009
Carolyn, you can import them all into Access and then use Access to delete the duplicates. There is a FIND DUPLICATES query wizard. Try that.
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duplicates Comment from Carolyn Quinn @ 7/28/2009
I have a table full of dupes.  Oh my goodness.  There are so many, yet they have their own uniqueness.  I am not sure how to delete them or if i should delete a few at a time; for instance, they all have an account name, Regional VP, Regional Director, Acct Number, budget number, Division VP and opening date.  These fields are all thed same for every account.  Then it has six programs, then they have about 8 brands, and then the 8 retail items.   This information is in Excel and i know it needs to go to Access, but i need to delete the dupes first.  It hard be cause one category says coffee, but there are 12 different coffees to choose from and one account could have all of them which is why the duplicate lines because each lines signifies another type of coffe.  I want to stop and start a database with relationships, but time won't permit me for this first report, but going forward i can.  What options do i have?
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Comment from Richard Rost @ 9/8/2008
Eric, I've got no idea. I'd have to see this database to tell you for sure. If the whole form just goes BLANK, that tells me that Access is out of system resources (memory). Have you tried just rebooting?
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Comment from Eric @ 8/31/2008
I am trying to create a form with multiple combo boxes from several different tables.  I can do it with one combo box from one table, but as soon as I add a third, the table becomes invisible in form view, even though I can still work with it in design view.  Any suggestions?
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