`information_schema.statistics.index_name`

mysql

type: VARCHAR NULL

type: VARCHAR NOT NULL

5.7

type: NULL

Note:

Index name. The primary key is always named PRIMARY.

5.1-10.8

type: VARCHAR NOT NULL

Note:

Index name. The primary key is always named PRIMARY.

type: VARCHAR(64) NULL

Note:

The name of the index. If the index is the primary key, then the value is always PRIMARY.

4-6.1

type: unknown

Note:

Name of the index.

1-21.2