drop table if exists t1;
select IF(0,"ERROR","this"),IF(1,"is","ERROR"),IF(NULL,"ERROR","a"),IF(1,2,3)|0,IF(1,2.0,3.0)+0 ;
IF(0,"ERROR","this")	IF(1,"is","ERROR")	IF(NULL,"ERROR","a")	IF(1,2,3)|0	IF(1,2.0,3.0)+0
this	is	a	2	2.0
CREATE TABLE t1 (st varchar(255) NOT NULL, u int(11) NOT NULL) ENGINE=MyISAM;
INSERT INTO t1 VALUES ('a',1),('A',1),('aa',1),('AA',1),('a',1),('aaa',0),('BBB',0);
select if(1,st,st) s from t1 order by s;
s
a
A
a
aa
AA
aaa
BBB
select if(u=1,st,st) s from t1 order by s;
s
a
A
a
aa
AA
aaa
BBB
select if(u=1,binary st,st) s from t1 order by s;
s
A
AA
BBB
a
a
aa
aaa
select if(u=1,st,binary st) s from t1 where st like "%a%" order by s;
s
A
AA
a
a
aa
aaa
explain extended select if(u=1,st,binary st) s from t1 where st like "%a%" order by s;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	7	Using where; Using filesort
Warnings:
Note	1003	select if((test.t1.u = 1),test.t1.st,cast(test.t1.st as char charset binary)) AS `s` from test.t1 where (test.t1.st like _latin1'%a%') order by if((test.t1.u = 1),test.t1.st,cast(test.t1.st as char charset binary))
select nullif(u=0, 'test') from t1;
nullif(u=0, 'test')
NULL
NULL
NULL
NULL
NULL
1
1
explain extended select nullif(u=0, 'test') from t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	7	
Warnings:
Note	1003	select nullif((test.t1.u = 0),_latin1'test') AS `nullif(u=0, 'test')` from test.t1
drop table t1;
select NULLIF(NULL,NULL), NULLIF(NULL,1), NULLIF(NULL,1.0), NULLIF(NULL,"test");
NULLIF(NULL,NULL)	NULLIF(NULL,1)	NULLIF(NULL,1.0)	NULLIF(NULL,"test")
NULL	NULL	NULL	NULL
select NULLIF(1,NULL), NULLIF(1.0, NULL), NULLIF("test", NULL);
NULLIF(1,NULL)	NULLIF(1.0, NULL)	NULLIF("test", NULL)
1	1.0	test
create table t1 (num  double(12,2));
insert into t1 values (144.54);
select sum(if(num is null,0.00,num)) from t1;
sum(if(num is null,0.00,num))
144.54
drop table t1;
create table t1 (x int, y int);
insert into t1 values (0,6),(10,16),(20,26),(30,10),(40,46),(50,56);
select min(if(y -x > 5,y,NULL)), max(if(y - x > 5,y,NULL)) from t1;
min(if(y -x > 5,y,NULL))	max(if(y - x > 5,y,NULL))
6	56
drop table t1;
create table t1 (a int);
insert t1 values (1),(2);
select if(1>2,a,avg(a)) from t1;
if(1>2,a,avg(a))
1.5000
drop table t1;
SELECT NULLIF(5,5) IS NULL, NULLIF(5,5) IS NOT NULL;
NULLIF(5,5) IS NULL	NULLIF(5,5) IS NOT NULL
1	0
CREATE TABLE t1 (a CHAR(10));
INSERT INTO t1 VALUES ('aaa'), (NULL), (''), ('bbb');
SELECT a, NULLIF(a,'') FROM t1;
a	NULLIF(a,'')
aaa	aaa
NULL	NULL
	NULL
bbb	bbb
SELECT a, NULLIF(a,'') FROM t1 WHERE NULLIF(a,'') IS NULL;
a	NULLIF(a,'')
NULL	NULL
	NULL
DROP TABLE t1;