Hi Dave!

I generally think of a key as any column(s) that uniquely identifies a record -
most often the primary key. The foreign key is something a bit different (and
not mentioned as often) since it need not be unique in the table where it is
defined, but must be unique in the table it references (i.e. defined as either a
primary key or with a unique constraint).

Set

Dave Bullar wrote:

> Thanks Helen.
> I may be nearly there, see my reply to Geoff. But I am somewhat thrown by
> your (and Jason's )frequent use of the word 'Key' . I am a self taught
> programmer (of data bases, I spent most of my 40 years of programming with
> assembler and embedded instrumentation systems) so I suspect there is a hole
> there in my education somewhere. I supose it stands for 'Key Field'. How
> about a definition of 'Key' for me ?
> I know about Primary 'Key' and Foreign 'Key' and that these are fields that
> must hold unique values and are often also an index, is that it ? Mind you,
> I do get hung up on terms. I got all behind at Maths because when the
> lecturer talked about 'weighting functions' I wrote it down as 'waiting
> functions' and could not follow the logic of it!
> regards Dave.