Question

From the table:

|   name   |   range   |
------------------------
| 'Range1' | '456-458' |
| 'Range2' |   '11-13' |

just trying to get this result:

|   name   |   range   | value |
--------------------------------
| 'Range1' | '456-458' |  456  |
| 'Range1' | '456-458' |  457  |
| 'Range1' | '456-458' |  458  |
| 'Range2' |   '11-13' |   11  |
| 'Range2' |   '11-13' |   12  |
| 'Range2' |   '11-13' |   13  |

made ​​the query which works fine if the source table has only one range:

WITH data AS (
    SELECT 'Range1' name, '456-458' range FROM dual
)
SELECT ROWNUM, name, range, LEVEL value
FROM data, dual
WHERE LEVEL >= to_number(SUBSTR(range, 1, INSTR(range,'-')-1))
CONNECT BY LEVEL <= to_number(SUBSTR(range, INSTR(range,'-')+1));

but returns tens of thousands of rows, if takes two ranges:

WITH data AS (
    SELECT 'Range1' name, '456-458' range FROM dual
    UNION
    SELECT 'Range2' name, '11-13' range FROM dual
)
SELECT ROWNUM, name, range, LEVEL value FROM data, dual
WHERE LEVEL >= to_number(SUBSTR(range, 1, INSTR(range,'-')-1))
CONNECT BY LEVEL <= to_number(SUBSTR(range, INSTR(range,'-')+1));

Is it possible to improve this query to get the required, or my approach is wrong initially?

Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production

Answer 1

in 11g you can use a recursive factored sub query for this type of thing.

SQL> with data as (select name, range,
  2                       to_number(substr(range, 1, instr(range,'-')-1)) from_val,
  3                       to_number(substr(range, instr(range,'-')+1)) to_val
  4                  from your_table),
  5  ranges (name, range, curr_val, from_val, to_val)
  6  as (select name, range, from_val, from_val, to_val
  7        from data
  8      union all
  9      select name, range, curr_val+1, from_val, to_val
 10        from ranges
 11       where curr_val < to_val)
 12  select name, range, curr_val
 13    from ranges
 14   order by name, curr_val;

NAME   RANGE     CURR_VAL
------ ------- ----------
Range1 456-458        456
Range1 456-458        457
Range1 456-458        458
Range2 11-13           11
Range2 11-13           12
Range2 11-13           13