Information Schema STATISTICS Table
The Information Schema STATISTICS table provides information about table indexes.
It contains the following columns:
| Column | Description |
|---|---|
TABLE_CATALOG | Always def. |
TABLE_SCHEMA | Database name. |
TABLE_NAME | Table name. |
NON_UNIQUE | 1 if the index can have duplicates, 0 if not. |
INDEX_SCHEMA | Database name. |
INDEX_NAME | Index name. The primary key is always named PRIMARY. |
SEQ_IN_INDEX | The column sequence number, starting at 1. |
COLUMN_NAME | Column name. |
COLLATION | A for sorted in ascending order, or NULL for unsorted. |
CARDINALITY | Estimate of the number of unique values stored in the index based on statistics stored as integers. Higher cardinalities usually mean a greater chance of the index being used in a join. Updated by the ANALYZE TABLE statement or myisamchk -a. |
SUB_PART | NULL if the whole column is indexed, or the number of indexed characters if partly indexed. |
PACKED | NULL if not packed, otherwise how the index is packed. |
NULLABLE | YES if the column may contain NULLs, empty string if not. |
INDEX_TYPE | Index type, one of BTREE, RTREE, HASH or FULLTEXT. See Storage Engine Index Types. |
COMMENT | Index comments from the CREATE INDEX statement. |
IGNORED | Whether or not an index will be ignored by the optimizer. See Ignored Indexes. From MariaDB 10.6.0. |
The SHOW INDEX statement produces similar output.
Example
SELECT * FROM INFORMATION_SCHEMA.STATISTICS\G
...
*************************** 85. row ***************************
TABLE_CATALOG: def
TABLE_SCHEMA: test
TABLE_NAME: table1
NON_UNIQUE: 1
INDEX_SCHEMA: test
INDEX_NAME: col2
SEQ_IN_INDEX: 1
COLUMN_NAME: col2
COLLATION: A
CARDINALITY: 6
SUB_PART: NULL
PACKED: NULL
NULLABLE:
INDEX_TYPE: BTREE
COMMENT:
INDEX_COMMENT:
...
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