Obtaining Information About Partitions It is possible to determine which partitions of a partitioned table are involved in a given  SELECT  query using EXPLAIN . The  partitions  column in the  EXPLAIN  output lists the partitions from which records would be matched by the query. Suppose that a table  trb1  is created and populated as follows: You can see which partitions are used in a query such as  SELECT * FROM trb1; , as shown here: In this case, all four partitions are searched. However, when a limiting condition making use of the partitioning key is added to the query, you can see that only those partitions containing matching values are scanned, as shown here: EXPLAIN   also provides information about keys used and possible keys: 4704 mysql>  ALTER TABLE trb1 ADD PRIMARY KEY (id); Query OK, 10 rows affected (0.03 sec) mysql>  EXPLAIN SELECT * FROM trb1 WHERE id < 5\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: trb1 partitions: p0,p1 type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 10 Extra: Using where mysql>  EXPLAIN SELECT * FROM trb1\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: trb1 partitions: p0,p1,p2,p3 type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 10 Extra: Using filesort CREATE TABLE trb1 (id INT, name VARCHAR(50), purchased DATE) PARTITION BY RANGE(id) ( PARTITION p0 VALUES LESS THAN (3), PARTITION p1 VALUES LESS THAN (7), PARTITION p2 VALUES LESS THAN (9), PARTITION p3 VALUES LESS THAN (11) ); INSERT INTO trb1 VALUES (1, ’desk organiser’, ’2003-10-15’), (2, ’CD player’, ’1993-11-05’), (3, ’TV set’, ’1996-03-10’), (4, ’bookcase’, ’1982-01-10’), (5, ’exercise bike’, ’2004-05-09’), (6, ’sofa’, ’1987-06-05’), (7, ’popcorn maker’, ’2001-11-22’), (8, ’aquarium’, ’1992-08-04’), (9, ’study desk’, ’1984-09-16’), (10, ’lava lamp’, ’1998-12-25’);