drop table if exists t1;select null,\N,isnull(null),isnull(1/0),isnull(1/0 = null),ifnull(null,1),ifnull(null,"TRUE"),ifnull("TRUE","ERROR"),1/0 is null,1 is not null;NULL	NULL	isnull(null)	isnull(1/0)	isnull(1/0 = null)	ifnull(null,1)	ifnull(null,"TRUE")	ifnull("TRUE","ERROR")	1/0 is null	1 is not nullNULL	NULL	1	1	1	1	TRUE	TRUE	1	1explain extended select null,\N,isnull(null),isnull(1/0),isnull(1/0 = null),ifnull(null,1),ifnull(null,"TRUE"),ifnull("TRUE","ERROR"),1/0 is null,1 is not null;id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables usedWarnings:Note	1003	select NULL AS `NULL`,NULL AS `NULL`,isnull(NULL) AS `isnull(null)`,isnull((1 / 0)) AS `isnull(1/0)`,isnull(((1 / 0) = NULL)) AS `isnull(1/0 = null)`,ifnull(NULL,1) AS `ifnull(null,1)`,ifnull(NULL,_latin1'TRUE') AS `ifnull(null,"TRUE")`,ifnull(_latin1'TRUE',_latin1'ERROR') AS `ifnull("TRUE","ERROR")`,isnull((1 / 0)) AS `1/0 is null`,(1 is not null) AS `1 is not null`select 1 | NULL,1 & NULL,1+NULL,1-NULL;1 | NULL	1 & NULL	1+NULL	1-NULLNULL	NULL	NULL	NULLselect NULL=NULL,NULL<>NULL,IFNULL(NULL,1.1)+0,IFNULL(NULL,1) | 0;NULL=NULL	NULL<>NULL	IFNULL(NULL,1.1)+0	IFNULL(NULL,1) | 0NULL	NULL	1.1	1select strcmp("a",NULL),(1<NULL)+0.0,NULL regexp "a",null like "a%","a%" like null;strcmp("a",NULL)	(1<NULL)+0.0	NULL regexp "a"	null like "a%"	"a%" like nullNULL	NULL	NULL	NULL	NULLselect concat("a",NULL),replace(NULL,"a","b"),replace("string","i",NULL),replace("string",NULL,"i"),insert("abc",1,1,NULL),left(NULL,1);concat("a",NULL)	replace(NULL,"a","b")	replace("string","i",NULL)	replace("string",NULL,"i")	insert("abc",1,1,NULL)	left(NULL,1)NULL	NULL	NULL	NULL	NULL	NULLselect repeat("a",0),repeat("ab",5+5),repeat("ab",-1),reverse(NULL);repeat("a",0)	repeat("ab",5+5)	repeat("ab",-1)	reverse(NULL)	abababababababababab		NULLselect field(NULL,"a","b","c");field(NULL,"a","b","c")0select 2 between null and 1,2 between 3 AND NULL,NULL between 1 and 2,2 between NULL and 3, 2 between 1 AND null;2 between null and 1	2 between 3 AND NULL	NULL between 1 and 2	2 between NULL and 3	2 between 1 AND null0	0	NULL	NULL	NULLexplain extended select 2 between null and 1,2 between 3 AND NULL,NULL between 1 and 2,2 between NULL and 3, 2 between 1 AND null;id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables usedWarnings:Note	1003	select (2 between NULL and 1) AS `2 between null and 1`,(2 between 3 and NULL) AS `2 between 3 AND NULL`,(NULL between 1 and 2) AS `NULL between 1 and 2`,(2 between NULL and 3) AS `2 between NULL and 3`,(2 between 1 and NULL) AS `2 between 1 AND null`SELECT NULL AND NULL, 1 AND NULL, NULL AND 1, NULL OR NULL, 0 OR NULL, NULL OR 0;NULL AND NULL	1 AND NULL	NULL AND 1	NULL OR NULL	0 OR NULL	NULL OR 0NULL	NULL	NULL	NULL	NULL	NULLSELECT (NULL OR NULL) IS NULL;(NULL OR NULL) IS NULL1select NULL AND 0, 0 and NULL;NULL AND 0	0 and NULL0	0select inet_ntoa(null),inet_aton(null),inet_aton("122.256"),inet_aton("122.226."),inet_aton("");inet_ntoa(null)	inet_aton(null)	inet_aton("122.256")	inet_aton("122.226.")	inet_aton("")NULL	NULL	NULL	NULL	NULLexplain extended select inet_ntoa(null),inet_aton(null),inet_aton("122.256"),inet_aton("122.226."),inet_aton("");id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables usedWarnings:Note	1003	select inet_ntoa(NULL) AS `inet_ntoa(null)`,inet_aton(NULL) AS `inet_aton(null)`,inet_aton(_latin1'122.256') AS `inet_aton("122.256")`,inet_aton(_latin1'122.226.') AS `inet_aton("122.226.")`,inet_aton(_latin1'') AS `inet_aton("")`create table t1 (x int);insert into t1 values (null);select * from t1 where x != 0;xdrop table t1;CREATE TABLE t1 (indexed_field int default NULL,KEY indexed_field (indexed_field));INSERT INTO t1 VALUES (NULL),(NULL);SELECT * FROM t1 WHERE indexed_field=NULL;indexed_fieldSELECT * FROM t1 WHERE indexed_field IS NULL;indexed_fieldNULLNULLSELECT * FROM t1 WHERE indexed_field<=>NULL;indexed_fieldNULLNULLDROP TABLE t1;create table t1 (a int, b int) engine=myisam;insert into t1 values(20,null);select t2.b, ifnull(t2.b,"this is null") from t1 as t2 left join t1 as t3 ont2.b=t3.a;b	ifnull(t2.b,"this is null")NULL	this is nullselect t2.b, ifnull(t2.b,"this is null") from t1 as t2 left join t1 as t3 ont2.b=t3.a order by 1;b	ifnull(t2.b,"this is null")NULL	this is nullinsert into t1 values(10,null);select t2.b, ifnull(t2.b,"this is null") from t1 as t2 left join t1 as t3 ont2.b=t3.a order by 1;b	ifnull(t2.b,"this is null")NULL	this is nullNULL	this is nulldrop table t1;CREATE TABLE t1 (a varchar(16) NOT NULL default '', b smallint(6) NOT NULL default 0, c datetime NOT NULL default '0000-00-00 00:00:00', d smallint(6) NOT NULL default 0);INSERT INTO t1 SET a = "", d= "2003-01-14 03:54:55";Warnings:Warning	1265	Data truncated for column 'd' at row 1UPDATE t1 SET d=1/NULL;Warnings:Warning	1265	Data truncated for column 'd' at row 1UPDATE t1 SET d=NULL;Warnings:Warning	1048	Column 'd' cannot be nullINSERT INTO t1 (a) values (null);ERROR 23000: Column 'a' cannot be nullINSERT INTO t1 (a) values (1/null);ERROR 23000: Column 'a' cannot be nullINSERT INTO t1 (a) values (null),(null);Warnings:Warning	1048	Column 'a' cannot be nullWarning	1048	Column 'a' cannot be nullINSERT INTO t1 (b) values (null);ERROR 23000: Column 'b' cannot be nullINSERT INTO t1 (b) values (1/null);ERROR 23000: Column 'b' cannot be nullINSERT INTO t1 (b) values (null),(null);Warnings:Warning	1048	Column 'b' cannot be nullWarning	1048	Column 'b' cannot be nullINSERT INTO t1 (c) values (null);ERROR 23000: Column 'c' cannot be nullINSERT INTO t1 (c) values (1/null);ERROR 23000: Column 'c' cannot be nullINSERT INTO t1 (c) values (null),(null);Warnings:Warning	1048	Column 'c' cannot be nullWarning	1048	Column 'c' cannot be nullINSERT INTO t1 (d) values (null);ERROR 23000: Column 'd' cannot be nullINSERT INTO t1 (d) values (1/null);ERROR 23000: Column 'd' cannot be nullINSERT INTO t1 (d) values (null),(null);Warnings:Warning	1048	Column 'd' cannot be nullWarning	1048	Column 'd' cannot be nullselect * from t1;a	b	c	d	0	0000-00-00 00:00:00	0	0	0000-00-00 00:00:00	0	0	0000-00-00 00:00:00	0	0	0000-00-00 00:00:00	0	0	0000-00-00 00:00:00	0	0	0000-00-00 00:00:00	0	0	0000-00-00 00:00:00	0	0	0000-00-00 00:00:00	0	0	0000-00-00 00:00:00	0drop table t1;create table t1 (a int not null, b int not null, index idx(a));insert into t1 values(1,1), (2,2), (3,3), (4,4), (5,5), (6,6),(7,7), (8,8), (9,9), (10,10), (11,11), (12,12);explain select * from t1 where a between 2 and 3;id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra1	SIMPLE	t1	range	idx	idx	4	NULL	2	Using whereexplain select * from t1 where a between 2 and 3 or b is null;id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra1	SIMPLE	t1	range	idx	idx	4	NULL	2	Using wheredrop table t1;select cast(NULL as signed);cast(NULL as signed)NULLcreate table t1(i int, key(i));insert into t1 values(1);insert into t1 select i*2 from t1;insert into t1 select i*2 from t1;insert into t1 select i*2 from t1;insert into t1 select i*2 from t1;insert into t1 select i*2 from t1;insert into t1 select i*2 from t1;insert into t1 select i*2 from t1;insert into t1 select i*2 from t1;insert into t1 select i*2 from t1;insert into t1 values(null);explain select * from t1 where i=2 or i is null;id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra1	SIMPLE	t1	ref_or_null	i	i	5	const	9	Using where; Using indexselect count(*) from t1 where i=2 or i is null;count(*)10alter table t1 change i i int not null;Warnings:Warning	1265	Data truncated for column 'i' at row 513explain select * from t1 where i=2 or i is null;id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra1	SIMPLE	t1	ref	i	i	4	const	7	Using indexselect count(*) from t1 where i=2 or i is null;count(*)9drop table t1;set names latin2;create table t1 selectnull as c00,if(1, null, 'string') as c01,if(0, null, 'string') as c02,ifnull(null, 'string') as c03,ifnull('string', null) as c04,case when 0 then null else 'string' end as c05,case when 1 then null else 'string' end as c06,coalesce(null, 'string') as c07,coalesce('string', null) as c08,least('string',null) as c09,least(null, 'string') as c10,greatest('string',null) as c11,greatest(null, 'string') as c12,nullif('string', null) as c13,nullif(null, 'string') as c14,trim('string' from null) as c15,trim(null from 'string') as c16,substring_index('string', null, 1) as c17,substring_index(null, 'string', 1) as c18,elt(1, null, 'string') as c19,elt(1, 'string', null) as c20,concat('string', null) as c21,concat(null, 'string') as c22,concat_ws('sep', 'string', null) as c23,concat_ws('sep', null, 'string') as c24,concat_ws(null, 'string', 'string') as c25,make_set(3, 'string', null) as c26,make_set(3, null, 'string') as c27,export_set(3, null, 'off', 'sep') as c29,export_set(3, 'on', null, 'sep') as c30,export_set(3, 'on', 'off', null) as c31,replace(null, 'from', 'to') as c32,replace('str', null, 'to') as c33,replace('str', 'from', null) as c34,insert('str', 1, 2, null) as c35,insert(null, 1, 2, 'str') as c36,lpad('str', 10, null) as c37,rpad(null, 10, 'str') as c38;show create table t1;Table	Create Tablet1	CREATE TABLE `t1` (  `c00` binary(0) default NULL,  `c01` varchar(6) character set latin2 default NULL,  `c02` varchar(6) character set latin2 default NULL,  `c03` varchar(6) character set latin2 NOT NULL default '',  `c04` varchar(6) character set latin2 default NULL,  `c05` varchar(6) character set latin2 default NULL,  `c06` varchar(6) character set latin2 default NULL,  `c07` varchar(6) character set latin2 default NULL,  `c08` varchar(6) character set latin2 default NULL,  `c09` varchar(6) character set latin2 default NULL,  `c10` varchar(6) character set latin2 default NULL,  `c11` varchar(6) character set latin2 default NULL,  `c12` varchar(6) character set latin2 default NULL,  `c13` varchar(6) character set latin2 default NULL,  `c14` char(0) character set latin2 default NULL,  `c15` char(0) character set latin2 default NULL,  `c16` varchar(6) character set latin2 default NULL,  `c17` varchar(6) character set latin2 default NULL,  `c18` char(0) character set latin2 default NULL,  `c19` varchar(6) character set latin2 default NULL,  `c20` varchar(6) character set latin2 default NULL,  `c21` varchar(6) character set latin2 default NULL,  `c22` varchar(6) character set latin2 default NULL,  `c23` varchar(9) character set latin2 default NULL,  `c24` varchar(9) character set latin2 default NULL,  `c25` varchar(12) character set latin2 default NULL,  `c26` varchar(7) character set latin2 default NULL,  `c27` varchar(7) character set latin2 default NULL,  `c29` varchar(381) character set latin2 default NULL,  `c30` varchar(317) character set latin2 default NULL,  `c31` varchar(192) character set latin2 default NULL,  `c32` char(0) character set latin2 default NULL,  `c33` varchar(3) character set latin2 default NULL,  `c34` varchar(3) character set latin2 default NULL,  `c35` varchar(3) character set latin2 default NULL,  `c36` varchar(3) character set latin2 default NULL,  `c37` varchar(10) character set latin2 default NULL,  `c38` varchar(10) character set latin2 default NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1drop table t1;select case 'str' when 'STR' then 'str' when null then 'null' end as c01,case 'str' when null then 'null' when 'STR' then 'str' end as c02,field(null, 'str1', 'str2') as c03,field('str1','STR1', null) as c04,field('str1', null, 'STR1') as c05,'string' in ('STRING', null) as c08,'string' in (null, 'STRING') as c09;c01	c02	c03	c04	c05	c08	c09str	str	0	1	2	1	1set names latin1;