[thelist] mysql - unique index combos

[David Siedband]

I have some index tables in mysql (v4.x) that have two fields, each 
being a unique ID from another table.  What I'd like to do is allow a 
combination of keys to be entered only once.

for example:

+-------------+-----------------+
| ProjectID  | DocumentID |
+-------------+-----------------+
| 327           | 440              |
| 446           | 743              |
| 226           | 444              |
| 446           | 743              |
| 226           | 444              |
+-------------+-----------------+

Is there a way to declare a unique index on these two fields, such that 
when someone tries to enter a combination that is already in the table 
it doesn't enter a duplicate entry?  ...or do I need to put this logic 
in my application instead?

thx
--
David Siedband
generation-xml.com