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MySQL NOT NULL Constraint

The NOT NULL constraint ensures that a column cannot have a NULL value. This constraint is used when a column must always have a value.

Example with Tamil Kings

CREATE TABLE tamil_kings_not_null (
    id INT AUTO_INCREMENT PRIMARY KEY,
    king_name VARCHAR(100) NOT NULL,
    reign_period VARCHAR(50) NOT NULL
);

Code Explanation: The king_name and reign_period columns cannot have NULL values, ensuring that every record in the tamil_kings_not_null table has these details.

Best Practices

  • Use NOT NULL for columns that must always have a value, such as primary identifiers or essential attributes.
  • Consider whether a default value is appropriate for the column if NULL is not allowed.

Key Takeaways

  • The NOT NULL constraint ensures that important columns are always filled with data.
  • Null values can cause errors or inconsistencies if not handled properly.
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