MySQL数据库

开发平台：

Visual C++

func_equal.result：源码内容

							drop table if exists t1,t2;
select 0<=>0,0.0<=>0.0,"A"<=>"A",NULL<=>NULL;
0<=>0	0.0<=>0.0	"A"<=>"A"	NULL<=>NULL
1	1	1	1
select 1<=>0,0<=>NULL,NULL<=>0;
1<=>0	0<=>NULL	NULL<=>0
0	0	0
select 1.0<=>0.0,0.0<=>NULL,NULL<=>0.0;
1.0<=>0.0	0.0<=>NULL	NULL<=>0.0
0	0	0
select "A"<=>"B","A"<=>NULL,NULL<=>"A";
"A"<=>"B"	"A"<=>NULL	NULL<=>"A"
0	0	0
create table t1 (id int, value int);
create table t2 (id int, value int);
insert into t1 values (1,null);
insert into t2 values (1,null);
select t1.*, t2.*, t1.value<=>t2.value from t1, t2 where t1.id=t2.id and t1.id=1;
id	value	id	value	t1.value<=>t2.value
1	NULL	1	NULL	1
select * from t1 where id <=>id;
id	value
1	NULL
select * from t1 where value <=> value;
id	value
1	NULL
select * from t1 where id <=> value or value<=>id;
id	value
drop table t1,t2;

						