FROM mysql.innodb_index_stats WHERE table_name like ’t1’; +------------+--------------+------------+-----------------------------------+ | index_name | stat_name | stat_value | stat_description | +------------+--------------+------------+-----------------------------------+ | PRIMARY | n_diff_pfx01 | 1 | a | | PRIMARY | n_diff_pfx02 | 5 | a,b | | PRIMARY | n_leaf_pages | 1 | Number of leaf pages in the index | | PRIMARY | size | 1 | Number of pages in the index | | i1 | n_diff_pfx01 | 1 | c | | i1 | n_diff_pfx02 | 2 | c,d | | i1 | n_diff_pfx03 | 2 | c,d,a | | i1 | n_diff_pfx04 | 5 | c,d,a,b | | i1 | n_leaf_pages | 1 | Number of leaf pages in the index | | i1 | size | 1 | Number of pages in the index | | i2uniq | n_diff_pfx01 | 2 | e | | i2uniq | n_diff_pfx02 | 5 | e,f | | i2uniq | n_leaf_pages | 1 | Number of leaf pages in the index | | i2uniq | size | 1 | Number of pages in the index | +------------+--------------+------------+-----------------------------------+ Configuring Optimizer Statistics for InnoDB The  stat_name  column shows the following types of statistics: • size : Where  stat_name = size , the  stat_value  column displays the total number of pages in the index. • n_leaf_pages : Where  stat_name = n_leaf_pages , the  stat_value  column displays the number of leaf pages in the index. • n_diff_pfx NN : Where  stat_name = n_diff_pfx01 , the  stat_value  column displays the number of distinct values in the first column of the index. Where  stat_name = n_diff_pfx02 , the  stat_value column displays the number of distinct values in the first two columns of the index, and so on. Where stat_name = n_diff_pfx NN , the  stat_description  column shows a comma separated list of the index columns that are counted. To further illustrate the  n_diff_pfx NN  statistic, which provides cardinality data, consider once again the t1  table example that was introduced previously. As shown below, the  t1  table is created with a primary index (columns  a ,  b ), a secondary index (columns  c ,  d ), and a unique index (columns  e ,  f ): CREATE TABLE t1 ( a INT, b INT, c INT, d INT, e INT, f INT, PRIMARY KEY (a, b), KEY i1 (c, d), UNIQUE KEY i2uniq (e, f) ) ENGINE=INNODB; After inserting five rows of sample data, table  t1  appears as follows: mysql>  SELECT * FROM t1; +---+---+------+------+------+------+ | a | b | c | d | e | f | +---+---+------+------+------+------+ | 1 | 1 | 10 | 11 | 100 | 101 | | 1 | 2 | 10 | 11 | 200 | 102 | | 1 | 3 | 10 | 11 | 100 | 103 | | 1 | 4 | 10 | 12 | 200 | 104 | | 1 | 5 | 10 | 12 | 100 | 105 | +---+---+------+------+------+------+ mysql>  SELECT index_name, stat_name, stat_value, stat_description FROM mysql.innodb_index_stats WHERE table_name like ’t1’ AND stat_name LIKE ’n_diff%’; When you query the  index_name ,  stat_name ,  stat_value , and  stat_description , where stat_name LIKE ’n_diff%’ , the following result set is returned: 3136