ORA-01722: Invalid number for Fr Locale for Oracle 11g - database

Question

I have a view named My_View which contains one varchar column having numeric decimal data.
While,select calculating avg in am getting error
ORA-01722: Invalid number for Fr Locale
Here is my oracle query which i tried but getting the error:
select (AVG(MY_COLUMN))
from MY_TABLE;
select TO_NUMBER((AVG(MY_COLUMN)), '90.9999', 'NLS_NUMERIC_CHARACTERS='',.''')
from MY_TABLE
GROUP BY MY_COLUMN;
How to get rid of this error?

Answer 1

Starting with Oracle 12.2, you can use the on conversion error clause of to_number() to return a default value when the conversion fails. This is handy for your use case: you can return null on conversion error, which aggregate function avg() will happily ignore.
select avg(
to_number(
my_column default null on conversion error,
'9999d9999',
'nls_numeric_characters = ''.,'''
)
) my_avg
from my_table;

Answer 2

Problem seems to be in data that isn't "numeric" (why do you keep numbers in VARCHAR2 columns)? For example, it contains '123A56'. What is AVG of that value?
A simple option is to use REGEXP_LIKE and perform numeric operations only on "valid" values. For example:
SQL> with test (col) as
2 (select '1234.56' from dual union all -- valid
3 select '131' from dual union all -- valid
4 select 'ABC' from dual union all -- invalid
5 select 'xy.23' from dual union all -- invalid
6 select '.3598' from dual union all -- invalid
7 select '12.34.56'from dual -- invalid
8 )
9 select col,
10 to_number(col, '9999D9999', 'nls_numeric_characters = ''.,''') col_as_num
11 from test
12 where regexp_like(col, '^\d+\.?\d+$');
COL COL_AS_NUM
-------- ----------
1234.56 1234,56
131 131
SQL>
Now you can AVG such values:
SQL> with test (col) as
2 (select '1234.56' from dual union all -- valid
3 select '131' from dual union all -- valid
4 select 'ABC' from dual union all -- invalid
5 select 'xy.23' from dual union all -- invalid
6 select '.3598' from dual union all -- invalid
7 select '12.34.56'from dual -- invalid
8 )
9 select avg(to_number(col, '9999D9999', 'nls_numeric_characters = ''.,''')) result
10 from test
11 where regexp_like(col, '^\d+\.?\d+$');
RESULT
----------
682,78
SQL>