Available in versions: Dev (3.20) | Latest (3.19)

HASH JOIN

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

The HASH JOIN algorithm uses a hash map to look up keys of one table when joining another. While this algorithm uses potentially large intermediary data structures, storing all data from tables in the hash maps (after applying predicates on them), it can join data in linear time, which is why it can be a fast choice for large data sets. An example:

SELECT *
FROM AUTHOR
INNER HASH JOIN BOOK
ON BOOK.AUTHOR_ID = AUTHOR.ID
 
create.select()
      .from(AUTHOR)
      .hashJoin(BOOK)
      .on(BOOK.AUTHOR_ID.eq(AUTHOR.ID))
      .fetch();

Dialect support

This example using jOOQ:

selectFrom(AUTHOR.hashJoin(BOOK).on(BOOK.AUTHOR_ID.eq(AUTHOR.ID)))

Translates to the following dialect specific expressions:

CockroachDB, SQLServer

SELECT
  AUTHOR.ID,
  AUTHOR.FIRST_NAME,
  AUTHOR.LAST_NAME,
  AUTHOR.DATE_OF_BIRTH,
  AUTHOR.YEAR_OF_BIRTH,
  AUTHOR.DISTINGUISHED,
  BOOK.ID,
  BOOK.AUTHOR_ID,
  BOOK.TITLE,
  BOOK.PUBLISHED_IN,
  BOOK.LANGUAGE_ID
FROM AUTHOR
  INNER HASH JOIN BOOK
    ON BOOK.AUTHOR_ID = AUTHOR.ID

Oracle

SELECT /*+leading(AUTHOR BOOK) use_hash(AUTHOR BOOK)*/
  AUTHOR.ID,
  AUTHOR.FIRST_NAME,
  AUTHOR.LAST_NAME,
  AUTHOR.DATE_OF_BIRTH,
  AUTHOR.YEAR_OF_BIRTH,
  AUTHOR.DISTINGUISHED,
  BOOK.ID,
  BOOK.AUTHOR_ID,
  BOOK.TITLE,
  BOOK.PUBLISHED_IN,
  BOOK.LANGUAGE_ID
FROM AUTHOR
  JOIN BOOK
    ON BOOK.AUTHOR_ID = AUTHOR.ID

YugabyteDB

SELECT /*+leading(AUTHOR BOOK) HashJoin(AUTHOR BOOK)*/
  AUTHOR.ID,
  AUTHOR.FIRST_NAME,
  AUTHOR.LAST_NAME,
  AUTHOR.DATE_OF_BIRTH,
  AUTHOR.YEAR_OF_BIRTH,
  AUTHOR.DISTINGUISHED,
  BOOK.ID,
  BOOK.AUTHOR_ID,
  BOOK.TITLE,
  BOOK.PUBLISHED_IN,
  BOOK.LANGUAGE_ID
FROM AUTHOR
  JOIN BOOK
    ON BOOK.AUTHOR_ID = AUTHOR.ID

ASE, Access, Aurora MySQL, Aurora Postgres, BigQuery, DB2, Derby, DuckDB, Exasol, Firebird, H2, HSQLDB, Hana, Informix, MariaDB, MemSQL, MySQL, Postgres, Redshift, SQLDataWarehouse, SQLite, Snowflake, Sybase, Teradata, Trino, Vertica

/* UNSUPPORTED */

(These are currently generated with jOOQ 3.20, see #10141), or translate your own on our website

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