Select distinct from multiple columns into one column

[Sunny]

Hello,
The problem is that I want to select distinct values from multiple columns of one table and want to select one column.
Say column1 has values: "first","second","third"
and column2 has values: "second","fifth","first"

I want to select unique from the above mentioned two columns so that result is like this:-
colname: "first","second","third","fifth"

Please suggest. Thanks in advance

[Rabbit]

The data should have been normalized in the first place.

I don't know if mysql supports unpivot but unpivot the data if you can. If you can't, you can use a union query to get the data in one column.

After normalizing the data, you can run your distinct.

[Sunny]

Thank you for posting Rabbit. Yes, it solved my problem. Thank you very much
I used :-
( select column1 as a from tbl_customer )
UNION Distinct
( select column2 as a from tbl_customer )


Though problem has been solved but I am thinking that in this statement I need to put select statement for that many times as many columns I have from the same table. Because I am selecting the table again and again, I think itmay take more time in executing.. there should be some other good way, something like
select ( column1 union column2 ) as result from table

Thanks

[Rabbit]

There is no other way. That is one of the drawbacks of using non-normalized data.