Oracle 11g Release 2

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CREATE TABLE test_table AS
    SELECT    10 AS Min,   121 AS Max FROM DUAL UNION ALL
    SELECT   122,          648 FROM DUAL UNION ALL
    SELECT  1200,         1599 FROM DUAL UNION ALL
    SELECT  1700,         1799 FROM DUAL union all
    
    SELECT 10050,        10106 FROM DUAL UNION ALL
    SELECT 10200,        11400 FROM DUAL UNION ALL
    SELECT 11450,        11500 FROM DUAL    
7 rows affected

CREATE TABLE reference_table AS
SELECT    50 AS Min, 106  AS Max FROM DUAL UNION ALL
SELECT   108,        108 FROM DUAL UNION ALL
SELECT   112,        166 FROM DUAL UNION ALL
SELECT   200,       1400 FROM DUAL union all

SELECT 10010,      10121 FROM DUAL UNION ALL
SELECT 10122,      10648 FROM DUAL UNION ALL
SELECT 11200,      11599 FROM DUAL;
7 rows affected

WITH minmax AS 
 ( -- create a list of all existing start/end values (may possible to simplify using Unpivot or Cross Apply?)
   SELECT Min AS val, -1 AS prio, 1 AS flag  -- main table, range start
   FROM test_table
   UNION ALL
   SELECT Max+1,   -1, -1                      -- main table, range end
   FROM test_table
   UNION ALL 
   SELECT Min, 1,  1                      -- reference table, adjusted range start
   FROM reference_table
   UNION ALL
   SELECT Max+1, 1, -1                      -- reference table, adjusted range end
   FROM reference_table
 )
, all_ranges AS 
 ( -- create all ranges from current to next row
   SELECT minmax.*,
     Lead(val) Over (ORDER BY val, prio desc, flag) AS next_val,  -- next value = end of range
     Sum(flag) Over (ORDER BY val, prio desc, flag ROWS Unbounded Preceding) AS Cnt -- how many overlapping periods exist
   FROM minmax
 )
SELECT val, next_val-1
FROM all_ranges
WHERE Cnt = 1           -- 1st level only
  AND prio + flag =  0  -- either (prio -1 and flag  1) = range start in base table
                        --     or (prio  1 and flag -1) = range end in ref table
ORDER BY 1


VAL
NEXT_VAL-1


10
49

107
107

109
111

167
199

1401
1599

1700
1799

10649
11199