What is the difference between MySQL PRIMARY KEY and UNIQUE constraint?

The following table will provide us the differences between PRIMARY KEY and UNIQUE constraint −

UNIQUE Constraint
1. Only one Primary key can be created on a table.
1. More than one UNIQUE Constraints can be added to a table.
2. Primary key creates clustered index by default.
2. UNIQUE Constraint creates a non-clustered index by default.
3. We cannot insert null values in the column which is defined as PRIMARY KEY.
3. We can insert null values in the column having a UNIQUE constraint.

Updated on: 19-Jun-2020


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