difference between a primary key and a unique key [Resolved]

Primary Key:

1) Primary Key creates clustered index by default

2) Primary Key doesn't allow nulls

Unique Key:

1) Unique Key creates non-clustered index by default

2) Unique Key allows only one null value

Saranya Boopathi, if this helps please login to Mark As Answer. | Alert Moderator

@Kirthiga

Small Correction on Primary Key definition! "Primary key will create with Clustered only if any of the column already doesn't have any Clustered in it. Other wise Primary key will be a Non-Clustered".

We should additional Cautious whenever using the word "DEFAULT"...! Because, It may be "NOT ALWAYS"

Do you agree ?

Cheers
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@Pandians

Thank u for your correction

Saranya Boopathi, if this helps please login to Mark As Answer. | Alert Moderator

primary key restrice duplicate values and null values each table can have only one primary key..

unique key restrict duplicate values and only one null values...

hope this will help....

sriram

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