Hitachi

Hitachi Advanced Database Application Development Guide


5.7 Grouping methods

There are two types of grouping methods:

Grouping is performed when the GROUP BY clause or the DISTINCT set function is specified. This section explains the grouping methods.

HADB automatically determines which grouping method to use. You can find out which grouping method was used by viewing the access path after the SQL statement is executed. For details about access paths, see the following subsections:

Note

You can prevent the application of global hash grouping by specifying a grouping method specification. For details about grouping method specifications, see Specification format and rules for GROUP BY clauses in the manual HADB SQL Reference.

Organization of this section