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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 joins and 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, EXASOL, H2, HSQLDB, MARIADB, MEMSQL, MYSQL, POSTGRES, REDSHIFT, SQLDATAWAREHOUSE, 
-- SQLSERVER, VERTICA, YUGABYTEDB
CREATE TABLE table (
  column1 int,
  CONSTRAINT fk
    FOREIGN KEY (column1)
    REFERENCES other_table (other_column1)
)

-- BIGQUERY
CREATE TABLE table (
  column1 int64
)

-- 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)
)

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

(These are currently generated with jOOQ 3.18, see #10141), or translate your own on our website

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