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

MERGE JOIN

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

The MERGE JOIN algorithm has similar characteristics as the HASH JOIN algorithm in that it reads all data of the tables involved (after applying predicates on them). But it does not require storing that data in memory, as it can "merge" all the tables' data in cases where it is fetched in a pre-sorted order, e.g. due to a covering index on the join key. An example:

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

Dialect support

This example using jOOQ:

selectFrom(AUTHOR.mergeJoin(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 MERGE JOIN BOOK
    ON BOOK.AUTHOR_ID = AUTHOR.ID

Oracle

SELECT /*+leading(AUTHOR BOOK) use_merge(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) MergeJoin(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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