SQL/PHP if input value exists, do not INSERT.
I'm trying to verify entries into my database using input comparison to a list I've compiled of 9,250 possible valid entries the user can make, that has been imported into a new table containing 3 columns. The column in question is "gamecode" under the table "disc_id".
If the value they use in the gamecode input field does not exist in the gamecode under disc_id, I'd like it to fail, maybe give them a relative error.
What are some methods to accomplish this?