SELECT CASE WHEN TRUNC(RN/2)=ROUND(RN/2)  THEN NULL ELSE 'X' END AS COL1,
       CASE WHEN TRUNC(RN/2)<>ROUND(RN/2) THEN NULL ELSE 'X' END AS COL2,
       CASE WHEN TRUNC(RN/2)=ROUND(RN/2)  THEN NULL ELSE 'X' END AS COL3,
       CASE WHEN TRUNC(RN/2)<>ROUND(RN/2) THEN NULL ELSE 'X' END AS COL4,
       CASE WHEN TRUNC(RN/2)=ROUND(RN/2)  THEN NULL ELSE 'X' END AS COL5
  FROM (
        SELECT ROW_NUMBER() OVER (ORDER BY COL1) AS RN,
               A.* 
          FROM TBL A
       );