2.24.3 Subquery execution method SQL optimization specification

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

(1) Function

The subquery execution method SQL optimization specification allows you to specify a subquery execution method for a subquery that occurs in a predicate.

(2) Format

Subquery-execution-method-SQL-optimization-specification:: = {HASH|NO HASH}

(3) Operands

HASH
Specifies the option for making the subquery execution method into a hash execution.
NO HASH
Specifies the option for making the subquery execution method into a non-hash execution.

(4) Rules

  1. Subquery execution method SQL optimization specification should be specified in a subquery that occurs in a predicate.
  2. 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-execution, see the HiRDB Version 8 UAP Development Guide.

(5) Notes

  1. For subquery execution methods, see the subquery execution method without external reference or the subquery execution method with external reference in the HiRDB Version 8 UAP Development Guide. Subquery execution methods can be checked by using the access path display utility.