I have an Oracle table and a column (col1) has type varchar2(12 byte). It has one row and value of col1 is 1234
col1
varchar2(12 byte)
1234
W
Oh, it is much better to convert to char rather than to numbers:
select * from table where col1 = to_char(1234)
When the col1 does not look like a number, to_number returns an error, stopping the query.