I took this one step further just for clarification. I added 2 ID_1 records for "D" with ID_2 values of "5" and "6" respectively.
I then created a SELECT query that displays only those records with multiple instances of ID_1.
Here's the SQL code:
SELECT Table3.ID_1, Table3.ID_2, Count(Table3_1.ID_1) AS CountOfID_1
FROM Table3 INNER JOIN Table3 AS Table3_1 ON Table3.ID_1 = Table3_1.ID_1
GROUP BY Table3.ID_1, Table3.ID_2
If you add the 2 extra records to your table that I did, and you create a query and paste in this SQL, you should get this result:
If this is correct, you can use this SELECT query to create a MAKE TABLE query to separate out the items, and then to create a DELETE query to delete these items from the main table if desired.
Hope this helps.
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