Question

How can I get previous or next product_id from table if I have only varchar to sort?
Example if I have PRODUCT_NO='20120033' and PRODUCT_REGISTRATION_NO='yellow', I would like to get the next record PRODUCT_ID which is 4 and I have PRODUCT_NO='20120033' and PRODUCT_REGISTRATION_NO='green', I would like to get the previous record PRODUCT_ID which is 3 How can I achieve this?

Thanks

Table structure and data are pasted below

CREATE TABLE MYTAB
(
  PRODUCT_ID               NUMBER,
  PRODUCT_NO               VARCHAR2(),
  PRODUCT_REGISTRATION_NO  VARCHAR2(32)
);


SET DEFINE OFF;
Insert into MYTAB
   (PRODUCT_ID, PRODUCT_NO, PRODUCT_REGISTRATION_NO)
 Values
   (3, '20120033', 'yellow');
Insert into MYTAB
   (PRODUCT_ID, PRODUCT_NO, PRODUCT_REGISTRATION_NO)
 Values
   (4, '20120033', 'green');
Insert into MYTAB
   (PRODUCT_ID, PRODUCT_NO, PRODUCT_REGISTRATION_NO)
 Values
   (5, '20120034', 'wine');
Insert into MYTAB
   (PRODUCT_ID, PRODUCT_NO, PRODUCT_REGISTRATION_NO)
 Values
   (6, '20120034', 'soda');
COMMIT;

Answer 1

Use the lag() and lead() functions:

select *
from (
    select product_id,
           product_no,
           product_registration_no, 
           lag(product_id) over (partition by product_no order by product_id) as prev_id,
           lead(product_id) over (partition by product_no order by product_id) as next_id
    from mytab
) 
where product_no='20120033' 
and product_registration_no='green' 

Note that the concept of “previous” and “next” only makes sense if you can specify a condition to sort on. That’s what the order by product_id in the window definition does.