char类型补空格引发的案子

不多说，都懂的：

create table test(
 col_char char(4)
);
insert into test values('a');
insert into test select 'a   'from dual;
insert into test values ('a000');
insert into test values('abc');
select col_char||'''' from test;
select replace(col_char,' ', '0') from test;
select * from test where col_char='a   ';
drop table test;