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#constraint

Commands grouped around the same concept, pattern, or recurring problem.

3 commands with this tag Browse related patterns quickly
intermediate ddl MySQL MariaDB SQL Server PostgreSQL SQLite

Add a Foreign Key Constraint

Enforce referential integrity by linking a column to the primary key of another table so orphaned rows cannot be inserted.

intermediate defining MySQL MariaDB SQL Server PostgreSQL SQLite

Enforce Uniqueness With CREATE UNIQUE INDEX

Create a unique index so the database rejects duplicate values in one or more columns.

intermediate defining MySQL MariaDB SQL Server PostgreSQL SQLite

Validate Column Values With CHECK

Use a `CHECK` constraint to reject rows whose values fall outside an allowed rule.