Applying where condition on Casted number coulmn in ORACLE from a inner query result - oracle

Question

For Sample purpose lets create a table with below schema and fill some sample values
CREATE TABLE games(ID INT ,Name VARCHAR(20));
INSERT INTO games(ID,Name) VALUES (2008,'Beijing');
INSERT INTO games(ID,Name) VALUES (2012,'London');
INSERT INTO games(ID,Name) VALUES (2012,12);
INSERT INTO games(ID,Name) VALUES (2012,654);
Output:
ID NAME
2008 Beijing
2012 London
2012 12
2012 654
In the above table we have both number and string data in the name column lets write a query that uses the REGX to filter only the numerical rows
SELECT TO_NUMBER(Name)as Trimmed FROM games where REGEXP_LIKE(Name, '(?<=\s|^)\d+(?=\s|$)', '')
Output:
TRIMMED
12
654
Now here is the problem if write a where clause of getting values greater than 12 from the above result it throws invalid number.
Select * from (SELECT TO_NUMBER(Name)as Trimmed FROM games where REGEXP_LIKE(Name, '(?<=\s|^)\d+(?=\s|$)', '')) T1 where T1.Trimmed >12 ;
I found this is how the oracle query planning works but is there any other way i can achieve this

Answer 1

This will work:
Select * from
(SELECT Name as Trimmed
FROM games where REGEXP_LIKE(Name, '(?<=\s|^)\d+(?=\s|$)', '')) T1
where to_number(T1.Trimmed) >12 ;
Unfortunately you need a subquery. It can't be done with one where.

Answer 2

This can be done in a single query:
with
inputs as (
select 2008 as id, 'Beijing' as name from dual union all
select 2012 , 'London' from dual union all
select 2012 , '12' from dual union all
select 2012 , '654' from dual
)
select id, name
from inputs
where translate(name, 'a0123456789', 'a') is null
and to_number(regexp_replace(name, '[^[:digit:]]', '')) > 12
;
ID NAME
---------- -------
2012 654
1 row selected.
regexp_replace removes all the characters except digits, so the test can be done regardless of what the name is. If there are no digits in the name, the result is NULL, which can be converted to number (it is still null).
The translate solution for testing for "all-digits" is more efficient than using regexp_like. The odd-looking 'a' in translate is needed due to an oddity in the translate function itself (see the documentation). This test is not needed if all the names are either "all letters" or "all digits" (if "all letters", the second test with regexp_replace would suffice); but the first test is needed if names like "Sydney 2000" are possible in the name column.