Firebird and SQL Server delete highest rows in groups - sql

Question

I need to delete the 3rd and greater records, sorted by product, type and display order, from the following tables:
Stockist table:
CREATE TABLE INVENTORYWEBSTOCKISTS
(
STOCKISTID NUMERIC(10,0) NOT NULL,
PRODUCTID NUMERIC(10,0) NOT NULL,
DISPLAYORDER NUMERIC(10,0),
CUSTOMERID NUMERIC(10,0),
CONSTRAINT PK_INVENTORYWEBSTOCKISTS PRIMARY KEY (STOCKISTID)
);
STOCKISTID is the unique autoinc column for the table and can be used as an ID. PRODUCTID and CUSTOMERID both reference other tables.
Customer table:
CREATE TABLE CUSTOMERS
(
CUSTOMERID NUMERIC(10,0) NOT NULL,
WEBSTOCKISTSTOCKISTTYPE VARCHAR(100),
CONSTRAINT PK_CUSTOMERS PRIMARY KEY (CUSTOMERID)
);
Customers table has records:
insert into CUSTOMERS (CUSTOMERID, WEBSTOCKISTSTOCKISTTYPE) values (1, 'Reseller');
insert into CUSTOMERS (CUSTOMERID, WEBSTOCKISTSTOCKISTTYPE) values (2, 'Reseller');
insert into CUSTOMERS (CUSTOMERID, WEBSTOCKISTSTOCKISTTYPE) values (3, 'Reseller');
insert into CUSTOMERS (CUSTOMERID, WEBSTOCKISTSTOCKISTTYPE) values (4, 'Installer');
insert into CUSTOMERS (CUSTOMERID, WEBSTOCKISTSTOCKISTTYPE) values (5, 'Installer');
insert into CUSTOMERS (CUSTOMERID, WEBSTOCKISTSTOCKISTTYPE) values (6, 'Installer');
insert into CUSTOMERS (CUSTOMERID, WEBSTOCKISTSTOCKISTTYPE) values (7, 'Installer');
Stockist table has records:
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (1, 1, -100, 1);
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (2, 1, -101, 2);
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (3, 1, -102, 3);
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (4, 1, -103, 4);
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (5, 1, -104, 5);
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (6, 1, -105, 6);
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (7, 1, -106, 7);
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (10, 2, -107, 3);
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (13, 2, -108, 6);
insert into INVENTORYWEBSTOCKISTS (STOCKISTID, PRODUCTID, DISPLAYORDER, CUSTOMERID) values (14, 2, -109, 7);
For the combined results:
select
INVENTORYWEBSTOCKISTS.STOCKISTID,
INVENTORYWEBSTOCKISTS.PRODUCTID,
INVENTORYWEBSTOCKISTS.DISPLAYORDER,
CUSTOMERS.WEBSTOCKISTSTOCKISTTYPE
from
INVENTORYWEBSTOCKISTS
left join
CUSTOMERS on CUSTOMERS.CUSTOMERID = INVENTORYWEBSTOCKISTS.CUSTOMERID
order by
INVENTORYWEBSTOCKISTS.PRODUCTID,
CUSTOMERS.WEBSTOCKISTSTOCKISTTYPE,
INVENTORYWEBSTOCKISTS.DISPLAYORDER
Output:
STOCKISTID, PRODUCTID, DISPLAYORDER, WEBSTOCKISTSTOCKISTTYPE
7, 1, -106, Installer
6, 1, -105, Installer
5, 1, -104, Installer
4, 1, -103, Installer
3, 1, -102, Reseller
2, 1, -101, Reseller
1, 1, -100, Reseller
14, 2, -109, Installer
13, 2, -108, Installer
10, 2, -107, Reseller
I need to delete the 3rd and above record for each product/stockist type group ordered by display order, so would expect it to delete rows 5, 4, and 1.
I have tried heaps of different queries from here and the web generally, I can't find anything that will group and order for the delete and work on both MS SQL and Firebird 1.5.
SQL Fiddle to experiment with: http://sqlfiddle.com/#!3/7101de/1
So after deleting, the table should look like:
Output:
STOCKISTID, PRODUCTID, DISPLAYORDER, WEBSTOCKISTSTOCKISTTYPE
7, 1, -106, Installer
6, 1, -105, Installer
3, 1, -102, Reseller
2, 1, -101, Reseller
14, 2, -109, Installer
13, 2, -108, Installer
10, 2, -107, Reseller
The delete should be executed as one query, so I can pass it to the server.
*** Edit:
Maybe to simplify, if I can do a select command that returns the STOCKISTID's to be deleted, I can then execute the delete commands seperately.
*** Edit 2:
As a test, I added the stockist type field to the INVENTORYWEBSTOCKISTS table, and can run this query:
SELECT INVENTORYWEBSTOCKISTS.STOCKISTID
FROM INVENTORYWEBSTOCKISTS IWS1
WHERE
(SELECT COUNT(*)
FROM INVENTORYWEBSTOCKISTS IWS2
WHERE IWS2.PRODUCTID = IWS1.PRODUCTID
AND IWS2.STOCKISTTYPE = IWS1.STOCKISTTYPE
AND IWS2.DISPLAYORDER <= IWS1.DISPLAYORDER) > 2
and return the correct fields (ie the ones that should be deleted). This was based on a question asked previously on SO.
As soon as I try and link in the CUSTOMER table as the query should be, it gives different results, less rows. Maybe someone might be able to help with that?

Answer 1

Try this, I have used ROW_NUMBER to eliminate your case (From what I understood from your question)
;WITH CTE AS(
SELECT ROW_NUMBER()OVER(PARTITION BY PRODUCTID,WEBSTOCKISTSTOCKISTTYPE
ORDER BY (SELECT 1) )SNO, INVENTORYWEBSTOCKISTS.*,
CUSTOMERS.WEBSTOCKISTSTOCKISTTYPE FROM
INVENTORYWEBSTOCKISTS
LEFT JOIN
CUSTOMERS ON INVENTORYWEBSTOCKISTS.CUSTOMERID = CUSTOMERS.CUSTOMERID
)
SELECT * FROM CTE WHERE SNO <3
Edit: From your comments:
;WITH CTE AS(
SELECT ROW_NUMBER()OVER(PARTITION BY PRODUCTID,WEBSTOCKISTSTOCKISTTYPE
ORDER BY (SELECT DISPLAYORDER) )SNO, INVENTORYWEBSTOCKISTS.*,
CUSTOMERS.WEBSTOCKISTSTOCKISTTYPE FROM
INVENTORYWEBSTOCKISTS
LEFT JOIN
CUSTOMERS ON INVENTORYWEBSTOCKISTS.CUSTOMERID = CUSTOMERS.CUSTOMERID
)
SELECT STOCKISTID FROM CTE WHERE SNO>2
If it is a problem with CTE
DELETE FROM INVENTORYWEBSTOCKISTS WHERE STOCKISTID IN (
SELECT STOCKISTID FROM (
SELECT ROW_NUMBER()OVER(PARTITION BY PRODUCTID,WEBSTOCKISTSTOCKISTTYPE
ORDER BY (SELECT DISPLAYORDER) )SNO, INVENTORYWEBSTOCKISTS.*,
CUSTOMERS.WEBSTOCKISTSTOCKISTTYPE FROM
INVENTORYWEBSTOCKISTS
LEFT JOIN
CUSTOMERS ON INVENTORYWEBSTOCKISTS.CUSTOMERID = CUSTOMERS.CUSTOMERID
) AS A WHERE SNO>2
)