求一MySql查询语句,该如何解决

求一MySql查询语句

SQL code

table a:aid na nb0   1  21   1  32   3  2查询结果：nab123

SQL code

select nabfrom (select na as nab from aunionselect nb as nab fromm a)Torder by T.nab
[解决办法]
错了
SQL code
select nabfrom (select distinct na as nab from aunionselect distinct nb as nab fromm a)Torder by T.na
[解决办法]
没有其它好方法了。