'#--------------------FN_DYNVARS_097_01-------------------------#' SET @@global.myisam_stats_method = nulls_equal; 'connect (con1,localhost,root,,,,)' 'connection con1' SELECT @@global.myisam_stats_method; @@global.myisam_stats_method nulls_equal SELECT @@session.myisam_stats_method; @@session.myisam_stats_method nulls_equal '#--------------------FN_DYNVARS_097_02-------------------------#' 'connection default' DROP TABLE IF EXISTS t1; CREATE TABLE t1 (a int, key (a)); INSERT INTO t1 VALUES (0),(1),(2),(3),(4); INSERT INTO t1 SELECT NULL FROM t1; 'default: NULLs considered unequal' SET myisam_stats_method=nulls_unequal; ANALYZE TABLE t1; Table Op Msg_type Msg_text test.t1 analyze status OK SHOW INDEX FROM t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 1 a 1 a A 10 NULL NULL YES BTREE INSERT INTO t1 VALUES (11); DELETE FROM t1 WHERE a=11; CHECK TABLE t1; Table Op Msg_type Msg_text test.t1 check status OK SHOW INDEX FROM t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 1 a 1 a A 10 NULL NULL YES BTREE 'Set nulls to be equal' SET myisam_stats_method=nulls_equal; INSERT INTO t1 VALUES (11); DELETE FROM t1 WHERE a=11; ANALYZE TABLE t1; Table Op Msg_type Msg_text test.t1 analyze status OK SHOW INDEX FROM t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 1 a 1 a A 5 NULL NULL YES BTREE INSERT INTO t1 VALUES (11); DELETE FROM t1 WHERE a=11; CHECK TABLE t1; Table Op Msg_type Msg_text test.t1 check status OK SHOW INDEX FROM t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 1 a 1 a A 5 NULL NULL YES BTREE 'Set nulls to be ignored' SET myisam_stats_method=nulls_ignored; SHOW variables LIKE 'myisam_stats_method'; Variable_name Value myisam_stats_method nulls_ignored drop TABLE t1; CREATE TABLE t1 ( a char(3), b char(4), c char(5), d char(6), key(a,b,c,d) ); INSERT INTO t1 VALUES ('bcd','def1', NULL, 'zz'); INSERT INTO t1 VALUES ('bcd','def2', NULL, 'zz'); INSERT INTO t1 VALUES ('bce','def1', 'yuu', NULL); INSERT INTO t1 VALUES ('bce','def2', NULL, 'quux'); ANALYZE TABLE t1; Table Op Msg_type Msg_text test.t1 analyze status OK SHOW INDEX FROM t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 1 a 1 a A 2 NULL NULL YES BTREE t1 1 a 2 b A 4 NULL NULL YES BTREE t1 1 a 3 c A 4 NULL NULL YES BTREE t1 1 a 4 d A 4 NULL NULL YES BTREE DELETE FROM t1; ANALYZE TABLE t1; Table Op Msg_type Msg_text test.t1 analyze status OK SHOW INDEX FROM t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 1 a 1 a A 0 NULL NULL YES BTREE t1 1 a 2 b A 0 NULL NULL YES BTREE t1 1 a 3 c A 0 NULL NULL YES BTREE t1 1 a 4 d A 0 NULL NULL YES BTREE SET myisam_stats_method=DEFAULT; DROP TABLE t1;