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Foreign keys

Applies to ✅ Open Source Edition   ✅ Express Edition   ✅ Professional Edition   ✅ Enterprise Edition

A foreign key is a tool that helps further normalise your database by guaranteeing that a referenced value exists in a parent table. In our sample database, it enforces the integrity of the BOOK.AUTHOR_ID reference. Besides integrity, it can be a very useful tool for optimising more sophisticated execution plans, e.g. to support JOIN elimination. In jOOQ, create foreign keys like this: 

// Create a new table with columns and unnamed constraints
create.createTable("table")
      .column("column1", INTEGER)
      .constraints(
          foreignKey("column1").references("other_table", "other_column1")
      )
      .execute();

// Create a new table with columns and named constraints (recommended if you want to alter the constraint)
create.createTable("table")
      .column("column1", INTEGER)
      .constraints(
          constraint("fk").foreignKey("column1").references("other_table", "other_column1")
      )
      .execute();

jOOQ's code generator will pick up foreign keys for a variety of purposes, including navigational methods, the ON KEY joinsand most prominently, the very powerful implicit joins.

Dialect support

This example using jOOQ:

createTable("table")
      .column("column1", INTEGER)
      .constraints(
          constraint("fk").foreignKey("column1").references("other_table", "other_column1")
      )

Translates to the following dialect specific expressions:

Access, DB2, Firebird, Hana, Teradata

CREATE TABLE table (
  column1 integer,
  CONSTRAINT fk FOREIGN KEY (column1) REFERENCES other_table (other_column1)
)

ASE, Sybase

CREATE TABLE table (
  column1 int NULL,
  CONSTRAINT fk FOREIGN KEY (column1) REFERENCES other_table (other_column1)
)

Aurora MySQL, Aurora Postgres, Derby, DuckDB, Exasol, H2, HSQLDB, MariaDB, MemSQL, MySQL, Postgres, Redshift, SQLDataWarehouse, SQLServer, SQLite, Vertica, YugabyteDB

CREATE TABLE table (
  column1 int,
  CONSTRAINT fk FOREIGN KEY (column1) REFERENCES other_table (other_column1)
)

BigQuery

CREATE TABLE table (
  column1 int64,
  CONSTRAINT fk FOREIGN KEY (column1) REFERENCES other_table (other_column1) NOT ENFORCED
)

ClickHouse

CREATE TABLE table (
  column1 Nullable(integer)
)
ENGINE Log()

CockroachDB

CREATE TABLE table (
  column1 int4,
  CONSTRAINT fk FOREIGN KEY (column1) REFERENCES other_table (other_column1)
)

Informix

CREATE TABLE table (
  column1 integer,
  FOREIGN KEY (column1) REFERENCES other_table (other_column1) CONSTRAINT fk
)

Oracle, Snowflake

CREATE TABLE table (
  column1 number(10),
  CONSTRAINT fk FOREIGN KEY (column1) REFERENCES other_table (other_column1)
)

Trino

CREATE TABLE table (
  column1 int
)
Generated with jOOQ 3.20. Translate your own SQL on our website

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