information_schema.statistics.cardinality

Note:

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.

Note:

TiDB does not use this field. The field value is always 0.

Note:

The estimated number of unique values ​​in the index. To update this value, execute ANALYZE TABLE.

Note:

Always NULL (unsupported by CockroachDB).