SELECT '1' AS RNK
       ,TO_CHAR(TO_DATE('0900','HH24MI')+ 30/(24*60),'HH24MI') AS TIME
  FROM DUAL;

위의 0900은 변수입니다. 입력받은 값에따라 12~13시는 제외되고 30분씩 증가시키려고합니다.

아래와같이 union all 안하고 쉽게 할수 있는게 있을꺼같아 질문올립니다.
 
SELECT '1' AS RNK,
       '0900' AS TIME
  FROM DUAL
SELECT '2' AS RNK,
       '0930' AS TIME
  FROM DUAL
SELECT '3' AS RNK,
       '1000' AS TIME
  FROM DUAL 
SELECT '4' AS RNK,
       '1030' AS TIME
  FROM DUAL 
SELECT '5' AS RNK,
       '1100' AS TIME
  FROM DUAL 
SELECT '6' AS RNK,
       '1130' AS TIME
  FROM DUAL
SELECT '7' AS RNK,
       '1300' AS TIME
  FROM DUAL
SELECT '8' AS RNK,
       '1330' AS TIME
  FROM DUAL 
SELECT '9' AS RNK,
       '1400' AS TIME
  FROM DUAL 
SELECT '10' AS RNK,
       '1430' AS TIME
  FROM DUAL;