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ALTER TABLE .. ADD UNIQUE
Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
All constraint types can be added with the ALTER TABLE statement. This includes UNIQUE constraints:
// Adding an unnamed constraint to a table
create.alterTable("table").add(unique("user_name")).execute();
// Adding a named constraint to a table
create.alterTable("table").add(constraint("uk").unique("user_name")).execute();
It is recommended to always provide a name with a constraint to simplify schema management. See also this section of the manual
Dialect support
This example using jOOQ:
alterTable("t").add(constraint("uk").unique("user_name"))
Translates to the following dialect specific expressions:
ASE, Access, Aurora MySQL, Aurora Postgres, BigQuery, ClickHouse, CockroachDB, DB2, Derby, Exasol, Firebird, H2, HSQLDB, Hana, MariaDB, MemSQL, MySQL, Oracle, Postgres, Redshift, SQLServer, Snowflake, Sybase, Teradata, Vertica, YugabyteDB
ALTER TABLE t ADD CONSTRAINT uk UNIQUE (user_name)
Informix
ALTER TABLE t ADD CONSTRAINT UNIQUE (user_name) CONSTRAINT uk
SQLDataWarehouse
ALTER TABLE t ADD CONSTRAINT uk UNIQUE (user_name) NOT ENFORCED
DuckDB, SQLite, Trino
/* UNSUPPORTED */
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