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What is the diffrence between unique and primary key constraints?
3 Answers
+ 1
the Primary Key does both, Makes values Unique and NOT NULL, it can only be used once per table, as of UNIQUE can be used multiple times in a table.
+ 1
primary keys are use to create foreign keys and normalize The table, that means, avoid duplicate data and improve performance
- 1
Unique can be null but primary key will never accept null.
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