c3 VARCHAR(25) ) PARTITION BY HASH(c1 + c2) PARTITIONS 4; 

The PARTITION_EXPRESSION  column in a PARTITIONS  table row for a partition from this table displays c1 + c2 , as shown here: 

mysql> SELECT DISTINCT PARTITION_EXPRESSION FROM INFORMATION_SCHEMA.PARTITIONS WHERE TABLE_NAME=’tp’ AND TABLE_SCHEMA=’test’; +----------------------+ | PARTITION_EXPRESSION | +----------------------+ | c1 + c2 | +----------------------+ 

• SUBPARTITION_EXPRESSION 

This works in the same fashion for the subpartitioning expression that defines the subpartitioning for a table as PARTITION_EXPRESSION  does for the partitioning expression used to define a table’s partitioning. 

If the table has no subpartitions, this column is NULL . 

• PARTITION_DESCRIPTION 

This column is used for RANGE and LIST partitions. For a RANGE  partition, it contains the value set in the partition’s VALUES LESS THAN  clause, which can be either an integer or MAXVALUE . For a LIST partition, this column contains the values defined in the partition’s VALUES IN  clause, which is a list of comma-separated integer values. 

For partitions whose PARTITION_METHOD  is other than RANGE  or LIST , this column is always NULL . 

• TABLE_ROWS 

The number of table rows in the partition. 

For partitioned InnoDB  tables, the row count given in the TABLE_ROWS  column is only an estimated value used in SQL optimization, and may not always be exact. 

For NDB  tables, you can also obtain this information using the ndb_desc  utility. 

• AVG_ROW_LENGTH 

The average length of the rows stored in this partition or subpartition, in bytes. This is the same as DATA_LENGTH  divided by TABLE_ROWS . 

For NDB  tables, you can also obtain this information using the ndb_desc  utility. 

• DATA_LENGTH 

The total length of all rows stored in this partition or subpartition, in bytes; that is, the total number of bytes stored in the partition or subpartition. 

For NDB  tables, you can also obtain this information using the ndb_desc  utility. 

• MAX_DATA_LENGTH 

The maximum number of bytes that can be stored in this partition or subpartition. 

