checking database before insert

[magyar]

Hello,

I've been trying to write a simple bit of PHP that will let me check a database before any new data is inserted.

For example, if a user is entered into a form on a website, how can I check the database to make sure that this user is not already in the DB?

Thanks,
M

[tomhath]

WIth most databases you could jsut try to SELECT it first, then INSERT if you don't find it. You should put both queries in a TRANSACTION block. But that doesn't work with mysql because it doesn't support transactions.

Another good alternative is to put a unique index on the column(s) that identify the user and try the INSERT. If it fails (because of a duplicate key) you can handle the error.