Using query results in further procedcures - sql

Question

I'm fairly new to SQL especially PL/SQL, I have a grasp of the basics but what i'm trying to do goes over my head. This is a small part of a larger system but I will focus on 3 tables Sale_Head, Sale_Line and Product. This work is being done in Orcale SQL developer.
http://imgur.com/OrfhM0g,i4pMnTx - Sale Table
http://imgur.com/OrfhM0g,i4pMnTx#1 - Product Table
(Im a newbie so i dont have enough rep to directly post images)
Im attempting to build up some procedures that process pending sales. Sales have a status in the Sale_Head which can either be p(pending), s(shipped), i(in progress), x(cancelled), or b(back orders). The procedure(s) need to find sales with a pending status (i've got that far in my code), then check the products stock levels are above the minimum level enough to complete the sale. If all these conditions are met pending sales become i (in progress) and if there is inadequate stock it comes backordered (b). I have a general idea of how to go about this, but when it comes having to referencing the product table using the foreign from sale_line I get confused.
--create or replace procedure Process_Products is
--begin
select Sale_Head.Sale_Num , Sale_Line.Product_Code as
from Sale_Head
inner join Sale_Line on
Sale_Head.Sale_Num = Sale_Line.SALE_NUM
where Sale_head.Status = 'P';
--if Sale_Line.Product_Code = Product.Product_Code >
--end;
This returns the product codes for orders that have a pending status, but now I need to check their stock levels in the product table and make adjustments.

Answer 1

Please correct me if I am wrong, but if you are saying "for those sales in a pending status where enough inventory exists to fulfill the order, change the status to i (in progress), otherwise not enough inventory exists, so change the status to b (backordered)", then the following should help:
-- This is a useful query to display what you need - debugging, use in cursor, etc
SELECT sh.Sale_Num, sl.Product_Code, sl.Quantity as QtyToBuy,
p.Stock_Count, p.Minimum_Level,
(Case When sl.Quantity <= p.Minimum_Level Then 'i'
Else 'b' end) as NewStatus
FROM Sale_Head sh
INNER JOIN Sale_Line sl
ON sh.Sale_Num = sl.SALE_NUM
INNER JOIN Product p
ON sl.Product_Code
WHERE Sale_head.Status = 'P';
The status code can be updated in one query if that is what you want:
--This query will actully do the update (if view is updatable)
UPDATE
(
SELECT sh.Status, (Case When sl.Quantity <= p.Minimum_Level Then 'i'
Else 'b' end) as NewStatus
FROM Sale_Head sh
INNER JOIN Sale_Line sl
ON sh.Sale_Num = sl.SALE_NUM
INNER JOIN Product p
ON sl.Product_Code
WHERE sh.Status = 'P'
) a
SET a.Status = a.NewStatus;
If the above view is not updatable, try this syntax:
--Otherwise try this syntax
UPDATE Sale_Head sh1 Set Sale_Head.Status =
SELECT (Case When sl.Quantity <= p.Minimum_Level Then 'i'
Else 'b' end) as NewStatus
FROM Sale_Head sh
INNER JOIN Sale_Line sl
ON sh.Sale_Num = sl.SALE_NUM
INNER JOIN Product p
ON sl.Product_Code
WHERE sh1.Sale_Num = sh.Sale_Num
)
WHERE Sale_Head.Status = 'P';