Lets have a table with two columns [col1, col2] with some values. values in col1 and col2 can be repeated. I would like to get number of unique values from both columns.

select
   count(distinct col1) as col1_unique,
   count(distinct col2) as col2_unique,
   count(distinct (col1, col2)) as total_unique
from myTable

that returns total_unique as combination of col1, col2 which is always bigger then a sum of col1_unique and col2_unique

as example:
table with rows:

1 1
1 2
1 3
2 1
2 2
2 2

should return col1_unique as 2, col2_unique as 3 and total_unique 3

how to correct the sql request ?