What are Difference between Primary and Unique key
Distinguish, differentiate, compare and explain what is the main difference between Primary and Unique key in database programming. Comparison and Differences.
Difference between Primary and Unique key
1 There is only one Primary key for a table. There may be more than one Unique Key for a table.
2 Primary Key can't contain a NULL value. Unique Key can contain only one NULL Value per column in a unique index column in SQL Server and DB2 (in Oracle Unique Key can have any number of NULL per column).
3 Primary Key creates a clustered index by default. Unique key creates a unique non-clustered index by default.
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Difference between Unique key vs Primary
Primary vs Unique key
Differences between Unique key vs Primary