content_image/707449.jpg content_image/707453.jpg content_image/707455.jpg
For unique indexes that include one or more NULL  columns of an NDB  table, the hash index can be used only to look up literal values, which means that IS [NOT] NULL  conditions require a full scan of the table. One workaround is to make sure that a unique index using one or more NULL  columns on such a table is always created in such a way that it includes the ordered index; that is, avoid employing USING HASH  when creating the index. 

If you specify an index type that is not valid for a given storage engine, but another index type is available that the engine can use without affecting query results, the engine uses the available type. The parser recognizes RTREE  as a type name, but currently this cannot be specified for any storage engine. 

<img src='content_image/707449.jpg'>

## Note 

Use of the index_type  option before the ON tbl_name  clause is deprecated; expect support for use of the option in this position to be removed in a future MySQL release. If an index_type  option is given in both the earlier and later positions, the final option applies. 

TYPE type_name  is recognized as a synonym for USING type_name . However, USING  is the preferred form. 

The following tables show index characteristics for the storage engines that support the index_type option. 

<img src='content_image/707453.jpg'>

<img src='content_image/707455.jpg'>

