sql - Select only distinct values from two columns from a table -

if have table such as

1  1 b  1  1 b  2 c  2 c

and want select distinct 2 columns get

1   2    b  c

how can word query? way concatenate columns , wrap them around distinct function operator?

you use union create table of values both columns:

select  col1 bothcolumns    yourtable union select  col2    yourtable

unlike union all, union removes duplicates, if come same side of union.

DIs