Postgres : get min and max rows count in many to many relation table

debugcn Published at Dev

Darshan Patel

I have mapping table for RFQ(request for quotation) and Vendor's bid amount.

rfq_vendor_mapping :

id  rfq_id(FK)  vendor_id(FK)   amount
---------------------------------------

 1      1           1            100
 2      1           2            50
 3      2           1            200
 4      2           3            300
 5      2           2            40
 6      3           4            70
 7      3           1            90
 8      3           2            250
 9      4           3            30
 10     5           1            500

In above table, I want analysis for how many times vendor has submitted minimum and maximum bid for each RFQ.

Expected Output :

vendor_id   min_bid_count   max_bid_count
-----------------------------------------
    1           1               2
    2           2               1
    3           1               2
    4           1               0

http://sqlfiddle.com/#!15/60198/1

Erwin Brandstetter

Compare the vendor's amount with min and max from a window function and run a conditional count on outer query level:

SELECT vendor_id
     , count(min_bid OR NULL) AS min_bid_count
     , count(max_bid OR NULL) AS max_bid_count
FROM  (
   SELECT vendor_id
        , amount = min(amount) OVER w AS min_bid
        , amount = max(amount) OVER w AS max_bid
   FROM   rfq_vendor_mapping
   WINDOW w AS (PARTITION BY rfq_id)
   ) sub
GROUP  BY 1
ORDER  BY 1;

SQL Fiddle.

Collected from the Internet

Please contact [email protected] to delete if infringement.