A Null question

[itm]

Hi,


Can someone tell me please if I am right here. If you are looking to have a unique key, and you take two columns to make a unique key, but one of th ecolumns have nulls in it; then it is not a unique key.
Example:
ID number, Reference number
Null , 1256
10456 , Null

AND in a number of cases I see things like in the table
Null , 1256
Null , 1256
Null , 1256

you could not say this is a unique key could you?
Thank you

[pbaldy]

I would agree with you; it's not a candidate for a key field if it can be Null.

[itm]

Thanks I appreciate your help.

[pbaldy]

No problemo.