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, 1) from t1;
nullif(u, 1)
NULL
NULL
NULL
NULL
NULL
0
0
explain extended select nullif(u, 1) 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`,1) AS `nullif(u, 1)` from `test`.`t1`
drop table t1;
select nullif(1,'test');
nullif(1,'test')
1
Warnings:
Warning	1292	Truncated incorrect DOUBLE value: 'test'
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` (
`id` int(11) NOT NULL ,
`date` int(10) default NULL,
`text` varchar(32) NOT NULL
);
INSERT INTO t1 VALUES (1,1110000000,'Day 1'),(2,1111000000,'Day 2'),(3,1112000000,'Day 3');
SELECT id, IF(date IS NULL, '-', FROM_UNIXTIME(date, '%d-%m-%Y')) AS date_ord, text FROM t1 ORDER BY date_ord ASC;
id	date_ord	text
1	05-03-2005	Day 1
2	16-03-2005	Day 2
3	28-03-2005	Day 3
SELECT id, IF(date IS NULL, '-', FROM_UNIXTIME(date, '%d-%m-%Y')) AS date_ord, text FROM t1 ORDER BY date_ord DESC;
id	date_ord	text
3	28-03-2005	Day 3
2	16-03-2005	Day 2
1	05-03-2005	Day 1
DROP TABLE t1;
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;
