If you do not have a client application that supports the BREAK command (which is not an SQL command but is a command for the SQL*Plus client or other similar clients) then you can use the ROW_NUMBER analytic function and CASE expressions:

SELECT CASE a_rn WHEN 1 THEN column_a END AS column_a,
       CASE b_rn WHEN 1 THEN column_b END AS column_b,
       column_c
FROM   (
  SELECT column_a,
         column_b,
         column_c,
         ROW_NUMBER() OVER (PARTITION BY column_a ORDER BY column_b, column_c)
           AS a_rn,
         ROW_NUMBER() OVER (PARTITION BY column_a, column_b ORDER BY column_c)
           AS b_rn
  FROM   table_name
)

Which, for the sample data:

CREATE TABLE table_name (Column_A, Column_B, Column_C) AS
SELECT '01', 'AB', 'col_amount' FROM DUAL UNION ALL
SELECT '01', 'AB', 'col_amount' FROM DUAL UNION ALL
SELECT '01', 'AB', 'col_amount' FROM DUAL UNION ALL
SELECT '02', 'OA', 'col_amount' FROM DUAL UNION ALL
SELECT '03', 'OE', 'col_amount' FROM DUAL UNION ALL
SELECT '03', 'OE', 'col_amount' FROM DUAL UNION ALL
SELECT '04', 'DB', 'col_amount' FROM DUAL;

Outputs:

COLUMN_A	COLUMN_B	COLUMN_C
01	AB	col_amount
null	null	col_amount
null	null	col_amount
02	OA	col_amount
03	OE	col_amount
null	null	col_amount
04	DB	col_amount

Note: In Oracle, NULL and an empty string are identical.

fiddle