Preventing Duplicate Entries in MySQL

[jawinn]

I have a web form that dumps form data into a DB. One of the fields is for email address. I would really like the form to kick back an error message if an email address is used that is already in the DB. My DB only has one table. What would the code be for that?

Thanks in advance,
J

[fenway]

There are lots of ways to handle this, depending on whether you can't have duplicates ever, or just do want to add new ones.  You can simply query the table before and see if another matching entry is found, or you can strictly enforce it with an index.

[jawinn]

This is an empty DB.  I will be empting it weekly and eventually daily.  I want to prevent ANY duplicates for a specific column.

[fenway]

Then go with a UNIQUE index.

[jawinn]

[quote author=fenway link=topic=110407.msg446343#msg446343 date=1159910890]
Then go with a UNIQUE index.
[/quote]

How do I add that to my script?

[fenway]

You have to modify your script to see if your INSERT failed.