This is not really a Perl problem. It's more a DB question.

You need to have a unique identifier (often: a primary key) and then formulate your query to select only the row with this unique identifier.

Never select everything from your DB to search for the data in your application.
Select only what you need from the DB and use it in your application.

"Livet är hårt" sa bonden.
"Grymt" sa grisen...