In relational databases, 'Unique Key' can be translated as 'unique key'

Many users think that the primary key and the unique key are the same because they can both uniquely identify a table, but the unique key and the primary key are different. Unique keys can accept null values, while primary keys cannot have null values.

Let us compare primary key and unique key and understand their concepts:

Purpose

Unique key is used to prevent duplicate values ​​in a column. The primary key provides uniqueness to the table.

Null values

Primary keys cannot accept null values; this makes primary keys different from unique keys, because unique keys allow one value to be NULL.

Quantity

A table can only have one primary key, but there can be multiple unique keys in the table.

Duplication

The unique key ensures that two rows of data in the database are not duplicated. In the case of unique keys, a row in the database can have null values.

Modification

The primary key cannot be modified, but the unique key can be modified.

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