text: SELECT
      CASE WHEN my_col IS NOT NULL THEN
          'Y'
      ELSE
          'N'
      END AS my_new_col,
      CASE WHEN TRIM(my_other_col) = 'confirmed' THEN
          'Y'
      ELSE
          'N'
      END AS new_col
  FROM
      my_table;
  
  SELECT DISTINCT ON (a, b)
      a,
      b,
      c
  FROM
      d
  ORDER BY
      a,
      b,
      c;
  
  SELECT DISTINCT
      a,
      b,
      b,
      c
  FROM
      d
  ORDER BY
      a,
      b,
      c;
  
  