How do select on 6 digit varchar field yymmdd index between 960530 & 120630

Question

I've been told that when you have a 6 digit date in the form of varchar2(6) yymmdd as an index for a table that you can't use a function on it or else it will mess up the index. For instance, you can do
SELECT cust_date
FROM customer
WHERE to_date(cust_date,'RRMMDD') BETWEEN '01-MAY-1995' AND '31-JUL-2012'
....but it will mess up the index and it will search through the whole table.
So, I'm looking for a way to formulate my SELECT statement to search on a date range on cust_date without messing up the index which is a varchar2(6) field containing yymmdd. The actual info that the user is entering is in the form of yymmdd so we can use that instead of the formatted '01-MAY-1995' AND '31-JUL-2012' if you like. And yes, this is in a pl/sql procedure so you can use variables if you like.
p.s. I didn't design the table nor am I allowed to alter it.

Answer 1

Hi,
if you work yet on this terrific date design, why not being consistent then?
create table customers as (select ename, hiredate from emp)
alter table customers add (cust_date varchar(6))
insert into customers (select ename||'20', add_months(hiredate, 360), null from emp)
14 row(s) inserted.
update customers
set cust_date = to_char(hiredate,'YYMMDD')
28 row(s) updated.
create index idx_cust_custdate on customers (cust_date)
Index created.
select cust_date, hiredate from customers
where
cust_date > '950501'
or
cust_date < '120731'
order by hiredate
CUST_DATE     HIREDATE
101217     12/17/2010
110220     02/20/2011
110222     02/22/2011
110402     04/02/2011
110501     05/01/2011
110609     06/09/2011
110908     09/08/2011
110928     09/28/2011
111117     11/17/2011
111203     12/03/2011
111203     12/03/2011
120123     01/23/2012
Operation     Options     Object     Rows     Time     Cost     Bytes     Filter
Predicates *     Access
Predicates
SELECT STATEMENT
                 13     1     5     182           
SORT
     ORDER BY           13     1     5     182           
CONCATENATION
TABLE ACCESS
     BY INDEX ROWID     CUSTOMERS     12     1     2     168           
INDEX
     RANGE SCAN     IDX_CUST_CUSTDATE     3     1     1                 "CUST_DATE"<'120731'
TABLE ACCESS
     BY INDEX ROWID     CUSTOMERS     1     1     2     14           
INDEX
     RANGE SCAN     IDX_CUST_CUSTDATE     3     1     1           LNNVL("CUST_DATE"<'120731')     "CUST_DATE">'950501'Just to be complete: you didnt ask for emulating the RR-date-format, did you?
regards
Edited by: chris227 on 17.07.2012 16:09