How can I search for duplicates in phpmyadmin?

I have a shopping cart, Cubecart to be exact.
How can I search the DB for duplicate data in a column?
Say the table is called “CC_inventory” and the column I want to use to find the duplicates is called “barcode”, what query would I use to list all the products with the same barcode?

The reason Im doing this is I have about 2000 items in the DB and I want to add about 900 more from a spreadsheet. I know for sure theres proably about 300 items in that spreadsheet that are already in the DB. I want to do an import of this data and then use phpmyadmin to find all the duplicates…

Thanks if you can help, Im not really up with Mysql stuff…

Edit: I found this query and I think it will do what I need.

select *
from wp_posts
group by post_content
having count(*) > 1

Something like that would tell you which barcodes have more than one entry, yes. But you can avoid running into the problem in the first place by putting a unique constraint on that column. Then when you try to INSERT another row with the same bar code, the query will fail.

yes, the thing is though I think my import system would fall over though, the unique constraint wouldnt allow me to import duplicate items along with new items.
I actually had this in place and have turned it off in preparation for this import.