Teradata - Get unique values among the column in a row

How to obtain unique values from a set of columns for each row in a table. Consider the following table structure:

COL1 | COL2 | COL3 | COL4
--------------------------
  1  |  1   |  2   |  3
  2  |  2   |  2   |  4
  4  |  5   |  6   |  7

The desired result should look like this:

COL1 | COL2 | COL3 | COL4
--------------------------
  1  |  2   |  3   | NULL
  2  |  4   | NULL | NULL
  4  |  5   |  6   |  7

I was able to achieve this by case statements by comparing each columns with each other. Are there any other way to do this?

You could use UNPIVOT (or UNION) + PIVOT

UNPIVOT - Get a row for each value of colN

Rank them and get the distinct.

PIVOT back to the original column list.

CREATE VOLATILE TABLE some_data
(
    COL1 INTEGER,
    COL2 INTEGER,
    COL3 INTEGER,
    COL4 INTEGER
) 
ON COMMIT PRESERVE ROWS;

INSERT INTO some_data (COL1, COL2, COL3, COL4) VALUES (1, 1, 2, 3);
INSERT INTO some_data (COL1, COL2, COL3, COL4) VALUES (2, 2, 2, 4);
INSERT INTO some_data (COL1, COL2, COL3, COL4) VALUES (4, 5, 6, 7);

with 
add_a_key as (
    select row_number() over ( order by 1) as a_key,
           sd.*
      from some_data sd),
unpivot_ranked as (
    select distinct
           a_key,
           val,
           dense_rank() over ( 
             partition by a_key
                 order by val ) as rn
      from add_a_key
      unpivot (
           val 
           for col in (col1, col2, col3, col4)
    ) as unpivoted
)
select col1,
       col2,
       col3,
       col4
  from unpivot_ranked
 pivot (
       sum(val) for rn in (1 as col1 ,
                           2 as col2,
                           3 as col3,
                           4 as col4)
       ) t
 order
    by col1;