Question

I have a table that contain some Inspection Data. Every commodity needs to be inspected every month. The goal here is to find the last inspected record for each month.

Table Inspection:

INSPECTION_I——–INSPECTION_TS

200————————— 10/20/2011

201—————————-10/24/2011

202—————————-10/26/2011

Table Product_Inspection:

INSPECTION_I——————ASSET_I

200————————————1000

201————————————2000

Table Box_Inspection

INSPECTION_I——–ASSET_I

202————————3000

Table Product

ASSET_I————ASSOCIATED_BOX_ASSET_I

1000—————————3000

Table BOX:

ASSET_I————OTHER_STUFF

3000——————–#####

Now in this case what I want is 201 and not 200. I tried to do MAX(to_char(inspection_ts, ‘mm/yyyy’)) but that is not helping. There is one more issue. For some reason, I keep getting the Cartesian in a case where a Product or a Box is inspected twice or more in a month. All I want is one inspection every month and it should be the last inspection for each month. I am really close to getting it but if someone can help, I would really appreciate it. I was able to get it done through a nested cursor but I don’t want that.

Answer 1

I tend to use analytic functions to do this kind of query. Something like:

with data as
(
    select 1 product_id, 100 inspection_id, to_date('09/04/2011', 'MM/DD/YYYY') inspection_date from dual union all
    select 1 product_id, 101 inspection_id, to_date('09/14/2011', 'MM/DD/YYYY') inspection_date from dual union all
    select 1 product_id, 103 inspection_id, to_date('10/04/2011', 'MM/DD/YYYY') inspection_date from dual union all
    select 1 product_id, 105 inspection_id, to_date('11/01/2011', 'MM/DD/YYYY') inspection_date from dual union all
    select 2 product_id, 102 inspection_id, to_date('09/24/2011', 'MM/DD/YYYY') inspection_date from dual union all
    select 2 product_id, 104 inspection_id, to_date('10/05/2011', 'MM/DD/YYYY') inspection_date from dual
)
select *
from 
(
    select
        product_id,
        inspection_id,
        inspection_date,
        row_number() over (
            partition by
                product_id,
                trunc(inspection_date, 'MM') -- Month
            order by
                inspection_date desc
        ) rn
    from
        data
)
where rn = 1 -- indicates last inspection date of the month for each product