preventing double entry in mySQL database

[brain]

I have made an insert PHP page for inserting a city into my database into the table tblPlace:
tblPlace
placeID
placeName
stateID

How can I prevent that someone inserts e.g. Amsterdam twice in the table ?

Greetz Brain

[cupid]

Hmm.. perhaps some clarifications would help us in coming up with a solution.

I'd imagine that placeID is the primary key.. what is StateID? Also, is there a list where users pick these locations or are they simply entering them?

If they're entering them instead of selecting these from a list.. I don't see an easier way to do this other than to query tblPlace and match each placeName with what they entered to see if it's already in it.

[MattR]

You can create a unique index on placeName. That should break when you try and insert dupe values (never tried it in MySQL).

[brain]

Thanks for the quick reply

[Defender1]

i've used the unique field when making a table.
seems to work pretty good. Should shoot a warning back if it exists already.

[brain]

Unique fields helps and it works. But how can I make my own error page in stead of:

Duplicate entry 'amsterdam' for key 2

Greetz Brain

[tubedogg]

if (mysql_error()) {
  if (strstr(mysql_error(),"Duplicate entry") {
    // custom error message/include page here
  } else {
    // echo normal error message? or do whatever you want
    echo mysql_error();
  }
} 

[brain]

OK, that helps, thank you !