Help with the a query -

Question

I have the table test1 with a date field stored as character 7 field.
(which is for CYYMMDD)
C - century indicator
and there are 3 rows in that table for testing purposes.
One of them has a value 9999999 which is a incorrect value for a given date.
I want to get all the rows with the value grater than 20020101 from that table.
Noted below are my table, values and query I used.
Can anyone help me with this?
create table test1(cr_date char(7);
SQL> desc test1
Name Null? Type
CR_DATE CHAR(7)
SQL> select * from test1;
CR_DATE
9999999
2021009
1980101
3 rows selected.
select
to_number(to_char(to_date((substr(cr_date,2,7)),'RRMMDD'),'RRRRMMDD'))
from test1 where cr_date<>'9999999' and
to_number(to_char(to_date((substr(cr_date,2,7)),'RRMMDD'),'RRRRMMDD'))>20020101
I get this error:
ERROR at line 2:
ORA-01843: not a valid month

Answer 1

But I don't have the control over this table because this is maintained by a real old
system in the MainframeI didn't say (or at least didn't mean to say) it was your fault. My point was that you need to have error handling in place for non-date values.
Note that Otto's solution will fail if any of the values in cr_date are non-numeric. Given that you have no control over what that column contains and that it is a string column you probably ought to handle that situation, unless you know for certain sure that everything in it will always be a number.
If you want to do so the easiest way would be to write a user defined function that applies a TO_DATE to the input argument and handles invalid dates by returning null or whatever takes your fancy. Other solutions may be more appropriate, depending on what you want to do with the data.
Cheers, APC