sql / intermediate
Snippet
Enforcing Multi-Column Uniqueness with Composite Indexes
Composite unique indexes ensure data integrity across multiple columns simultaneously while improving lookup speeds for combined WHERE clause conditions. The index prevents duplicate combinations of user IDs and session tokens.
snippet.sql
sql
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CREATE UNIQUE INDEX idx_unique_user_sessionON user_sessions (user_id, session_token);
Breakdown
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CREATE UNIQUE INDEX idx_unique_user_session
Creates a unique index named idx_unique_user_session that rejects duplicate key entries.
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ON user_sessions (user_id, session_token);
Applies the unique index across the tuple of user_id and session_token columns in user_sessions.