A hash index must have a primary index. Unlike other base tables, you do not use the keywords PRIMARY INDEX to specify the primary index for a hash index.
The following table explains how the primary index for a hash index is defined:
|Hash Index||Primary Index for the Hash Index Uses this Column Set|
|Does not define a BY clause||Primary index of the base table to which the hash index refers.|
|Specifies a BY clause and an ORDER BY clause||Column set specified in the column_name_2 set in the BY clause.
These columns must also be defined in the column_name_1 set.
Rows in a hash index defined with this type of primary index are ordered either by row hash or by numeric value, depending on what you specify in the ORDER BY clause.