Yesterday I was importing some data I downloaded. When creating a new table I tried to convert two columns with latitude and longitude, stored as VARCHAR2, to numbers (in order to use them in the SDO_GEOMETRY constructor). The create table as select (CTAS) statement failed with ORA-01722. Problem is it does not tell you which line or what value is the offender. You may turn on some tracing with event 1722, but using regular expression is much easier:
select longitude
from data_import
where regexp_instr(longitude,'\d+.\d{7}') = 0;
This will show you rows that does match the format used in the to_number function. Which in this case was '99.9999999'. Turned out that some of the rows had "(blank)" in them... they were updated to NULL.
Oracle database has support for regular expressions in theses functions:
