Hello Everyone,
I would like to know What’s the Difference between a Primary Key and a Unique Key?
Kate
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Hello Everyone,
I would like to know What’s the Difference between a Primary Key and a Unique Key?
Kate
Hi Kate,
Both primary key and unique key enforce uniqueness of the column on which they are defined. But by default, the primary key creates a clustered index on the column, whereas unique key creates a non-clustered index by default. Another major difference is that primary key doesn’t allow NULLs, but unique key allows one NULL only.
Nimol
Programmer
Corbin Creative Databases, LLC
http://www.corbincreative.com
You can have only one primary key in a table but can have multiple unique keys, which by the way violates 3rd normal form.