ALTER TABLE

ALTER TABLE tablename ADD CONSTRAINT constraintname UNIQUE (columns);

See also

• ALTER, ALTER DATABASE, ALTER DEFAULT PRIVILEGES
• SQL, NewSQL: GraphQL (2015), SQLite, select, insert, select count, Distributed SQL, TablePlus, Cache hit ratio, pg_stat_user_tables, EXPLAIN, Index (PostgreSQL), DDL, SQL/MED, Group by, List users, SQL Injection, SQLAlchemy, CREATE USER, CREATE ROLE, EXPLAIN, ALTER DATABASE, REVOKE, NOLOCK, NOWAIT, EXISTS, Unique constraint