2.24.2 Join method SQL optimization specification

Organization of this subsection
(1) Function
(2) Format
(3) Operands
(4) Rules
(5) Notes

(1) Function

The join method SQL optimization specification allows you to specify a join method for a joined table.

(2) Format

Join-method-SQL-optimization-specification::= BY {NEST|HASH|MERGE}

(3) Operands

NEST
This option can be specified when the join method is a nested-loop join.
If the inner table is a base table or a named derived table based on a base table, the join method becomes a nested-loop join.
HASH
This option can be specified when making the join method into a hash-join.
MERGE
This option can be specified when making the join method into a merge-join.

(4) Rules

  1. Specifying HASH requires the same preparations as specifying execution of a hash-join or a subquery hash for the SQL extension optimizing option. For preparations for applying either hash-join or subquery-hash-join, see the HiRDB Version 9 UAP Development Guide.

(5) Notes

  1. For join methods, see the HiRDB Version 9 UAP Development Guide. Join methods can be checked by using the access path display utility.