One-to-One Relationship in SQL

One-to-One Relationship in SQL — a practical guide to SQL one-to-one relationship with clear examples you can reuse in real projects.

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Short description

Often used for optional profile extensions.

1:1 sketch

CREATE TABLE user_profiles (
  user_id INT UNSIGNED PRIMARY KEY,
  bio TEXT,
  FOREIGN KEY (user_id) REFERENCES users(id)
);