Duplicate data often creeps in when multiple users add data to the Access database at the same time or if the database wasn’t designed to check for duplicates. Duplicate data can be either multiple tables containing the same data or two records containing just some fields (columns) with similar data. Here’s how you can locate duplicate records for a desktop database.
Note: These methods do not apply to Access web apps.
Find duplicate records
To find duplicate records using the Query Wizard, follow these steps.
On the Create tab, in the Queries group, click Query Wizard. Note, if you're using Access 2007, on the Create tab, in the Other group, click Query Wizard.
In the New Query dialog, click Find Duplicates Query Wizard > OK.
In the list of tables, select the table you want to use and click Next.
Select the fields that you want to match and click Next.
In the list of available fields, select the field or fields that contain the data that you want to update and click Next.
Accept the suggested query name or enter a name, and click Finish to run the query.
After you locate duplicate records, you can either edit or Delete duplicate records with a query.
To locate duplicate records from multiple tables, create a union query.