By 25/02/2016 1 Comments

What Is UNIQUE Constraint In SQL?

  • SQL UNIQUE constraint uniquely identifies each record/row in a database table.
  • SQL UNIQUE constraint prevents to insert duplicate value in a same table column.
  • Multiple SQL UNIQUE constraints can be applied at single table.

Example: MySQL

country_id BIGINT(11),
country_name VARCHAR(200) NOT NULL,
country_location VARCHAR(200) NOT NULL,
country_zipcode INT(60),
UNIQUE (country_zipcode)


  • In above example UNIQUE constraint is added to country_zipcode column.

Posted in: Sql

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