Using distinct on a column and doing order by on another column gives an error

Question

I have a table: abc_test with columns n_num, k_str.

This query doesnt work:

    select distinct(n_num) from abc_test order by(k_str)

B

Answer 1

The first query is impossible. Lets explain this by example. we have this test:

n_num k_str
2     a
2     c
1     b

select distinct (n_num) from abc_test is

2
1

Select n_num from abc_test order by k_str is

2
1
2

What do you want to return

select distinct (n_num) from abc_test order by k_str?

it should return only 1 and 2, but how to order them?