CREATE INDEX Statement Index Class Index Type Stores NULL VALUES Permits Multiple NULL Values IS NULL Scan Type IS NOT NULL Scan Type SPATIAL N/A No No N/A N/A Index Class Index Type Stores NULL VALUES Permits Multiple NULL Values IS NULL Scan Type IS NOT NULL Scan Type Primary key BTREE No No N/A N/A Unique BTREE Yes Yes Index Index Key BTREE Yes Yes Index Index Primary key HASH No No N/A N/A Unique HASH Yes Yes Index Index Key HASH Yes Yes Index Index Index Class Index Type Stores NULL VALUES Permits Multiple NULL Values IS NULL Scan Type IS NOT NULL Scan Type Primary key BTREE No No Index Index Unique BTREE Yes Yes Index Index Key BTREE Yes Yes Index Index Primary key HASH No No Table (see note 1) Table (see note 1) Unique HASH Yes Yes Table (see note 1) Table (see note 1) Key HASH Yes Yes Table (see note 1) Table (see note 1) Table 13.4 MEMORY Storage Engine Index Characteristics Table 13.5 NDB Storage Engine Index Characteristics Table note: 1.  USING HASH  prevents creation of an implicit ordered index. • WITH PARSER  parser_name This option can be used only with  FULLTEXT  indexes. It associates a parser plugin with the index if full- text indexing and searching operations need special handling.  InnoDB  and  MyISAM  support full-text parser plugins. If you have a  MyISAM  table with an associated full-text parser plugin, you can convert the table to  InnoDB  using  ALTER TABLE . See Full-Text Parser Plugins and Writing Full-Text Parser Plugins for more information. 2527