Getting rate for my report

Question

Hi All,
I would like some help with this query. This is my sample code:
create table myReport(
report_id integer,
product_class_id integer,
place_id integer,
fy integer);
insert into myReport(report_id, product_class_id, place_id, fy)
values (1, 1, 1, 2012);
insert into myReport(report_id, product_class_id, place_id, fy)
values (2, 1, 2, 2011);
insert into myReport(report_id, product_class_id, place_id, fy)
values (3, 1, 3, 2011);
insert into myReport(report_id, product_class_id, place_id, fy)
values (4, 2, 2, 2012);
insert into myReport(report_id, product_class_id, place_id, fy)
values (5, 2, 5, 2011);
insert into myReport(report_id, product_class_id, place_id, fy)
values (6, 3, 1, 2012);
insert into myReport(report_id, product_class_id, place_id, fy)
values (7, 4, 1, 2012);
create table myRates(
rate_id integer,
product_class_id integer,
place_id integer)
insert into myRates(rate_id, product_class_id, place_id)
values(1, 1, 1);
insert into myRates(rate_id, product_class_id, place_id)
values(2, 1, 2);
insert into myRates(rate_id, product_class_id, place_id)
values(3, 1, null);
insert into myRates(rate_id, product_class_id, place_id)
values(4, 2, 1);
insert into myRates(rate_id, product_class_id, place_id)
values(5, 2, 2);
insert into myRates(rate_id, product_class_id, place_id)
values(6, 2, null);
create table myRatesByYear(
rate_id integer,
fy integer,
rate integer)
insert into myRatesByYear(rate_id,fy,rate)
values(1, 2011, 5);
insert into myRatesByYear(rate_id,fy,rate)
values(1, 2012, 15);
insert into myRatesByYear(rate_id,fy,rate)
values(2, 2011, 6);
insert into myRatesByYear(rate_id,fy,rate)
values(2, 2012, 12);
insert into myRatesByYear(rate_id,fy,rate)
values(3, 2011, 7);
insert into myRatesByYear(rate_id,fy,rate)
values(3, 2012, 14);
insert into myRatesByYear(rate_id,fy,rate)
values(4, 2011, 8);
insert into myRatesByYear(rate_id,fy,rate)
values(4, 2012, 16);
insert into myRatesByYear(rate_id,fy,rate)
values(5, 2011, 9);
insert into myRatesByYear(rate_id,fy,rate)
values(5, 2012, 18);
insert into myRatesByYear(rate_id,fy,rate)
values(6, 2011, 2);
insert into myRatesByYear(rate_id,fy,rate)
values(6, 2012, 4);As you see I have a rate table by rate_id, product_class_id, place_id and year
select r.rate_id, r.product_class_id, r.place_id, y.fy, y.rate
from myRates r
join myRatesByYear y on y.rate_id = r.rate_id;
rate_id     product_class_id     place_id     fy     rate
1     1     1     2011     5
1     1     1     2012     15
2     1     2     2011     6
2     1     2     2012     12
3     1     NULL     2011     7
3     1     NULL     2012     14
4     2     1     2011     8
4     2     1     2012     16
5     2     2     2011     9
5     2     2     2012     18
6     2     NULL     2011     2
6     2     NULL     2012     4I would like to get the rate for my report table base. The search for the rate first will be base on product_class_id, year and place_id, second if the report row match the product_class_id and year but not place_id it should get the default rate (in my rate table the place_id is null).
Last if the report row doesn't match any key the result should be zero.
This is my result query, how can I do this query?
report_id     product_class_id     place_id     fy rate
1     1     1     2012   15
2     1     2     2011   6
3     1     3     2011   7
4     2     2     2012   18
5     2     5     2011   2
6     3     1     2012   0
7     4     1     2012   0I try to do a function by don't know how to handle the default place_id (null)
I hope this is clear... Thanks!
Best,

Answer 1

Hi,
Here's one way to do that:
WITH   got_r_num     AS
     SELECT    re.*
     ,       y.rate
     ,       ROW_NUMBER () OVER ( PARTITION BY  re.report_id
                                  ORDER BY          r.place_id        NULLS LAST
                         )           AS r_num
     FROM           myreport       re
     LEFT OUTER JOIN  myrates        r  ON   r.product_class_id  = re.product_class_id
                                           AND  NVL ( r.place_id
                                         , re.place_id
                                       )              = re.place_id
        LEFT OUTER JOIN  myratesbyyear  y  ON     y.rate_id         = r.rate_id
                                        AND     y.fy              = re.fy
SELECT    report_id
,        product_class_id
,        place_id
,       fy
,       NVL ( rate
           , 0
           )          AS rate
FROM       got_r_num
WHERE       r_num     = 1
ORDER BY  report_id
;Output:
`      PRODUCT
REPORT  _CLASS PLACE
   _ID     _ID   _ID         FY       RATE
     1       1     1       2012         15
     2       1     2       2011          6
     3       1     3       2011          7
     4       2     2       2012         18
     5       2     5       2011          2
     6       3     1       2012          0
     7       4     1       2012          0This outer-joins the myreport table to the result set you posted, keeping only the rows where myrates.place_id is either NULL or the same as myreport.place_id. From there, it's a matter of picking the best match, when there is a choice, where rows with non-NULL myrates.place_id are better than rows with NULL myrates.place_id. Picking the best row, however "best" is defined, is often a job for the analytic ROW_NUMBER function.