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WITH t AS
(
SELECT 'M' equipment, '11:00' starttime, '12:00' endtime FROM dual
UNION ALL SELECT 'C', '11:30', '12:30' FROM dual
UNION ALL SELECT 'O', '11:10', '13:00' FROM dual
UNION ALL SELECT 'M', '15:00', '15:20' FROM dual
UNION ALL SELECT 'O', '16:00', '17:00' FROM dual
UNION ALL SELECT 'M', '12:00', '12:30' FROM dual
UNION ALL SELECT 'M', '16:30', '18:00' FROM dual
UNION ALL SELECT 'M', '18:00', '19:30' FROM dual
UNION ALL SELECT 'O', '18:20', '19:00' FROM dual
UNION ALL SELECT 'C', '17:10', '20:00' FROM dual
UNION ALL SELECT 'M', '19:30', '20:00' FROM dual
UNION ALL SELECT 'K', '19:30', '20:00' FROM dual
UNION ALL SELECT 'L', '13:00', '14:00' FROM dual
)
SELECT equipment, starttime, endtime
     , LISTAGG(stm||'~'||etm, ',') WITHIN GROUP(ORDER BY grp) tm
  FROM (SELECT equipment, starttime, endtime
             , grp
             , MIN(stm) stm
             , MAX(etm) etm
          FROM (SELECT equipment, starttime, endtime
                     , stm, etm
                     , SUM(flag) OVER(PARTITION BY equipment, starttime ORDER BY stm) grp
                  FROM (SELECT a.equipment, a.starttime, a.endtime
                             , b.stm, b.etm
                             , DECODE(LAG(etm)
                                      OVER(PARTITION BY equipment, starttime ORDER BY stm)
                                      , stm, 0, 1) flag
                          FROM t a
                             , (SELECT stm
                                     , LEAD(stm) OVER(ORDER BY stm) etm
                                     , SUM(cnt) OVER(ORDER BY stm) cnt
                                  FROM (SELECT DECODE(s, 1, starttime, endtime) stm
                                             , SUM(s) cnt
                                          FROM t
                                             , (SELECT 3-LEVEL*2 s
                                                  FROM dual CONNECT BY LEVEL <= 2)
                                         GROUP BY DECODE(s, 1, starttime, endtime)
                                        )
                                ) b
                         WHERE b.stm(+) >= a.starttime
                           AND b.etm(+) <= a.endtime
                           AND b.cnt(+) > 1
                        )
                )
         GROUP BY equipment, starttime, endtime, grp
        )
 GROUP BY equipment, starttime, endtime
 ORDER BY starttime
;