suresh What is the difference between primary key and unique key constraints in Oracle?
In Oracle, the primary key and unique key constraints are both used to enforce uniqueness in a column or a set of columns in a table. The focus keyword that sets them apart is their level of restriction and purpose.
Primary Key Constraint: The primary key constraint is used to uniquely identify each record in a table and does not allow NULL values. There can be only one primary key constraint defined for a table.
Unique Key Constraint: The unique key constraint also enforces uniqueness in a column or a set of columns, but it allows NULL values. Unlike the primary key constraint, multiple unique key constraints can be defined for a table.
It is essential to choose between a primary key and a unique key constraint based on the specific requirements of the data model and the level of uniqueness needed for the columns in Oracle databases.
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