Question

I’m trying to get a query which would show distributors that haven’t sell anything in 90 days, but the problem I get is with NULL values. It seems PostgreSQL ignores null values, even when I queried to show it (or maybe I did it in wrong way).

Let say there are 1000 distributors, but with this query I only get 1 distributor, but there should be more distributors that didn’t sell anything, because if I write SQL query to show distributors that sold by any amount in the last 90 days, it shows about 500. So I wonder where are those other 499? If I understand correctly, those other 499, didn’t have any sales, so all records are null and are not showed in query.

Does anyone know how to make it show null values of one table where in relation other table is not null? (like partners table (res_partner) is not null, but sale_order table (sales) or object is null? (I also tried to filter like so.id IS NULL, but in such way I get empty query)

Code of my query:

(
SELECT
    min(f1.id) as id,
    f1.partner as partner,
    f1.sum1
       FROM
    (
       SELECT
          min(f2.id) as id,
          f2.partner as partner,
          sum(f2.null_sum) as sum1
       FROM
    (
    SELECT
          min(rp.id) as id,
          rp.search_name as partner,
     CASE
       WHEN
             sol.price_subtotal IS NULL
       THEN
             0
       ELSE
             sol.price_subtotal
     END as null_sum
    FROM
          sale_order as so,
          sale_order_line as sol,
          res_partner as rp
    WHERE
    sol.order_id=so.id and
    so.partner_id=rp.id
    and
    rp.distributor=TRUE
    and
    so.date_order <= now()::timestamp::date
    and
    so.date_order >= date_trunc('day', now() - '90 day'::interval)::timestamp::date
    and 
    rp.contract_date <= date_trunc('day', now() - '90 day'::interval)::timestamp::date
    GROUP BY
    partner,
    null_sum
   )as f2
   GROUP BY
   partner
  ) as f1
WHERE
sum1=0
GROUP BY
partner,
sum1
)as fld

EDIT: 2012-09-18 11 AM.

I think I understand why Postgresql behaves like this. It is because of the time interval. It checks if there is any not null value in that inverval. So it only found one record, because that record had sale order with zero (it was not converted from null to zero) and part which checked for null values was just skipped. If I delete time interval, then I would see all distributors that didn’t sell anything at all. But with time interval for some reason it stops checking null values and looks if there are only not null values.

So does anyone know how to make it check for null values too in given interval?.. (for the last 90 days to be exact)

Answer 1

Aggregates like sum() and and min() do ignore NULL values. This is required by the SQL standard and every DBMS I know behaves like that.

If you want to treat a NULL value as e.g. a zero, then use something like this:

sum(coalesce(f2.null_sum, 0)) as sum1

But as far as I understand you question and your invalid query you actually want an outer join between res_partner and the sales tables.

Something like this:

SELECT min(rp.id) as id,
       rp.search_name as partner,
       sum(coalesce(sol.price_subtotal,0)) as price_subtotal
FROM res_partner as rp 
  LEFT JOIN sale_order as so ON so.partner_id=rp.id and rp.distributor=TRUE
  LEFT JOIN sale_order_line as sol ON sol.order_id=so.id 
WHERE so.date_order <= CURRENT_DATE
  and so.date_order >= date_trunc('day', now() - '90 day'::interval)::timestamp::date
  and rp.contract_date <= date_trunc('day', now() - '90 day'::interval)::timestamp::date
GROUP BY rp.search_name

I’m not 100% sure I understood your problem correctly, but it might give you a headstart.