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MySQL UNIQUE Constraint

The UNIQUE constraint ensures that all values in a column are unique, preventing duplicate values. You can apply it to one or more columns.

Example with Tamil Kings

CREATE TABLE tamil_kings_unique (
    id INT AUTO_INCREMENT PRIMARY KEY,
    king_name VARCHAR(100) UNIQUE,
    reign_period VARCHAR(50)
);

Code Explanation: The king_name column must contain unique values, ensuring that no two kings in the tamil_kings_unique table have the same name.

Best Practices

  • Use UNIQUE for columns that require distinct values, like usernames or email addresses.
  • Consider using composite unique keys for columns that require combined uniqueness.

Key Takeaways

  • The UNIQUE constraint ensures data uniqueness within a column.
  • Multiple unique columns can be defined in a single table.
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