primary and unique key constraints

[southbeach]

What is the difference between these two?

Thank you all for your time!

--
SouthBeach

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The good thing about not knowing is the opportunity to learn - Yours truly, 2008.

 

[max1x]

Well first off if you have a PRIMARY KEY defined it needs to be UNIQE to begin with.

What other constraints are you inquring about?i.e can it be an int, varchar, text...etc?

 

[r937]

no, you do not need to define a primary key as unique as well, because a primary key is unique by definition

the main difference is that a primary key may not be null, whereas a unique key may



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