what's the difference between a primary key and a unique key? : Sql server database administration
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Answer Posted / Manoj Kumar Tiwari
A Primary Key is a column or group of columns in a table that uniquely identifies each row. It must contain unique, non-null values and cannot be changed once set. A Unique Key is similar to a Primary Key but can be composed of multiple columns and allows for null values (if all columns allow nulls). However, if the table has a Primary Key, it cannot have more than one Unique Key.
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