drop table if exists t1,t2;
create table t1(str varchar(10) default 'def',strnull varchar(10),intg int default '10',rel double default '3.14');
insert into t1 values ('','',0,0.0);
select default(str), default(strnull), default(intg), default(rel) from t1;
default(str)	default(strnull)	default(intg)	default(rel)
def	NULL	10	3.14
explain extended select default(str), default(strnull), default(intg), default(rel) from t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
Warnings:
Note	1003	select default(`test`.`t1`.`str`) AS `default(str)`,default(`test`.`t1`.`strnull`) AS `default(strnull)`,default(`test`.`t1`.`intg`) AS `default(intg)`,default(`test`.`t1`.`rel`) AS `default(rel)` from `test`.`t1`
select * from t1 where str <> default(str);
str	strnull	intg	rel
		0	0
explain select * from t1 where str <> default(str);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
drop table t1;