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, ClickHouse, DB2, Derby, DuckDB, Exasol, Firebird, H2, HSQLDB, Hana, Informix, MariaDB, MemSQL, MySQL, Postgres, Redshift, SQLDataWarehouse, SQLite, Snowflake, Sybase, Teradata, Trino, Vertica
/* UNSUPPORTED */
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