Hi, I get the ORA- 01722 error (invalid number string) when I try to convert varchar2 to number using to_number function. Case 1: I have all numbers in varchar2 but it seems there is some character value too. Is there a way that I can know that field is. The table is huge (>13,000,000 rows) Case 2: When I query "select to_number(oci_id) from oci_tb; ", I don't get any error. But I get ORA - 01722 when I query "select oci_id from oci_tb where to_number(oci_id) > 10000; ". I have no clue why I get error when where cluse is used. Any suggestion? Thanks -- //www.freelists.org/webpage/oracle-l