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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