PL/SQL Decode

CREATE OR REPLACE FORCE VIEW VEW_TABLE_NAME ("ID", "COLUMN_X")
AS
  SELECT "ID",
    concat(concat(COLUMN_X,    ' '),
    decode(COLUMN_X,    null, null, decode(COLUMN_Y,    1, 'kg', 2, 'gr'))) AS COLUMN_X,
FROM TABLE_NAME;