Basic Question : Primary Key versus NoDuplicates

[Swamp Thing]

What is the difference in Access' behavior between these two cases:

1. Setting a certain field as a primary key
2. Setting it to Indexed-No-Duplicates

In both cases, that end of the join is displayed as "one-to-.."
In both cases, the values are unique.

So how do they differ in practice?

 

[dk]

Well I guess you could have more than one column set to Yes (No Duplicates) whereas you can only designate one primary key. Also, when you compact and repair each table will be sorted by primary key. It's also easy for others to understand your database if you have correctly specified a primary key for each table. As for performance, I'd be surprised if there is a great difference between the two although you'd need to do some testing to be certain.

 

[SydneyGeek]

Sometimes you'll find that Access won't permit data entry if there is no primary key.

Denis

 

[Swamp Thing]

Thanks, folks!

Thanks, DK, Sydney. Your replies helped me understand this concept.