Select only distinct values from two columns from a table

Question

If I have a table such as

1 A

1 B

1 A

1 B

2 C

2 C

And I want to select distinct from the two columns so that I would get

1 

2 

A

B

C

How can I word my query? Is the only way to concatenate the columns and wrap them around a distinct function operator?

Answer 1

You could use a union to create a table of all values from both columns:

select  col1 as BothColumns
from    YourTable
union
select  col2
from    YourTable

Unlike union all, union removes duplicates, even if they come from the same side of the union.