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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;
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