使用 subQuery SQL 选择最大值

Question

Using the below query, I am selecting the ItemName, Description from Items Table and QuantityInStock, CurrentPrice from ItemsStock Table. And also trying to fetch the VendorName for each Item from Vendors Table using PurchaseInvoices and ItemsReceived Table Relation. Now the problem is I want to fetch the VENDOR who provided the MOST QUANTITY for a particular item.

I mean let's say an ITEM ABC was provided by 3 VENDORS V1, V2, and V3. V3 provided 90 times (He provided most quantity). Now I want to show him in VendorName column. Likewise for each item show the vendor who provided that item most times.

Query I am using (I think this subquery needs to be changed)

SELECT Items.Name
    ,Max(Items.Description) AS Description
    ,Max(ItemsStock.Quantity) AS QuantityInStock
    ,Max(ItemsStock.CurrentPrice) AS CurrentPrice
    ,Max(Vendors.VendorName)
FROM ItemsSold
INNER JOIN Items ON ItemsSold.ItemSoldID = Items.ItemID
INNER JOIN ItemsStock ON ItemsSold.ItemSoldID = ItemsStock.ItemID
INNER JOIN Vendors ON Vendors.VendorID = (
        SELECT max(PI.VendorID)
        FROM ItemReceived IR
        JOIN PurchaseInvoices PI ON IR.PurchaseInvoiceID = PI.PurchaseInvoiceID
        WHERE IR.ItemID = Items.ItemID
        GROUP BY IR.ItemID
        )
GROUP BY Items.Name

Answer 1

Something like this:

Select 
  Items.Name,
  Items.Description,
  ItemsStock.Quantity,
  ItemsStock.CurrentPrice,
  Vendors.VendorName
From 
ItemsSold
INNER Join Items On ItemsSold.ItemSoldID = Items.ItemID
INNER JOIN ItemsStock On ItemsSold.ItemSoldID = ItemsStock.ItemID
INNER JOIN 
(
  SELECT *, ROW_NUMBER() OVER(PARTITION BY a.ItemID ORDER BY sumProvided DESC) rown FROM
  (
    SELECT PI.VendorID, IR.ItemID, SUM(IR.Quantity) as sumProvided
    FROM ItemReceived IR
    INNER JOIN PurchaseInvoices PI on IR.PurchaseInvoiceID = PI.PurchaseInvoiceID
    GROUP BY PI.VendorID, IR.ItemID
  ) a
) v
ON v.ItemID = Items.ItemID AND v.rown = 1
INNER JOIN Vendors ON Vendors.VendorID = v.VendorID

Here there's an inner query that sums up the supplies of a particular item by each vendor, then an outer query that numbers the rows with 1 = the highest supplier

In the outermost query we cut it to just the rows that were rown=1 (the most vending vendor

I removed the outer group by because I can't see how it makes sense to aggregate these things. You should note that your question is hard to write a test for, because you haven't included sample data and expected output.. but this is a general tactic for "find the highest X and return other column Y from the same row"

You will have to replace SUM(PI.PURCHASE_QUANTITY) with something relevant yourself - you didn't give any clues as to what the structure of the PI table was

I presume that going from v.VendorID to Vender.VendorName will be easy enough for you to do

---

OK, so - debugging SQLs 101

I assert that this should work:

Select 
  *
From 
--ItemsSold
--INNER Join Items On ItemsSold.ItemSoldID = Items.ItemID
--INNER JOIN ItemsStock On ItemsSold.ItemSoldID = ItemsStock.ItemID
--INNER JOIN
(
  SELECT *, ROW_NUMBER() OVER(PARTITION BY a.ItemID ORDER BY sumProvided DESC) rown FROM
  (
    SELECT PI.VendorID, IR.ItemID, SUM(IR.Quantity) as sumProvided
    FROM ItemReceived IR
    INNER JOIN PurchaseInvoices PI on IR.PurchaseInvoiceID = PI.PurchaseInvoiceID
    GROUP BY PI.VendorID, IR.ItemID
  ) a
) v
--ON v.ItemID = Items.ItemID AND v.rown = 1

I just put a SELECT *, then stripped out all the tables apart from one - the one that is doing th most work. So.. Does it return any records?

If not, then the join is faulty (there are no records in PI that relate to IR), or there really are no records in PI or IR

Fix it so this returns rows

Next question Does the query return a 1 in rown column, for the suppliers who shipped you the most of a particular item?

If not, something is wonky with the records - take a look. If so, we're all good

Join the other tables back in one at a time:

Select 
  *
From 
--ItemsSold
/*INNER Join*/ Items /*On ItemsSold.ItemSoldID = Items.ItemID*/
--INNER JOIN ItemsStock On ItemsSold.ItemSoldID = ItemsStock.ItemID
INNER JOIN
(
  SELECT *, ROW_NUMBER() OVER(PARTITION BY a.ItemID ORDER BY sumProvided DESC) rown FROM
  (
    SELECT PI.VendorID, IR.ItemID, SUM(IR.Quantity) as sumProvided
    FROM ItemReceived IR
    INNER JOIN PurchaseInvoices PI on IR.PurchaseInvoiceID = PI.PurchaseInvoiceID
    GROUP BY PI.VendorID, IR.ItemID
  ) a
) v
ON v.ItemID = Items.ItemID AND v.rown = 1

Keep going until you suddenly lose records that you weren't expecting would disappear...

:

Select 
  *
From 
ItemsSold
INNER Join Items On ItemsSold.ItemSoldID = Items.ItemID
--INNER JOIN ItemsStock On ItemsSold.ItemSoldID = ItemsStock.ItemID
INNER JOIN
(
  SELECT *, ROW_NUMBER() OVER(PARTITION BY a.ItemID ORDER BY sumProvided DESC) rown FROM
  (
    SELECT PI.VendorID, IR.ItemID, SUM(IR.Quantity) as sumProvided
    FROM ItemReceived IR
    INNER JOIN PurchaseInvoices PI on IR.PurchaseInvoiceID = PI.PurchaseInvoiceID
    GROUP BY PI.VendorID, IR.ItemID
  ) a
) v
ON v.ItemID = Items.ItemID AND v.rown = 1

Maybe all the items in "items sold" and all the items in "items received" don't match up! (Maybe you only ever sold stuff you haven't replaced, or sold things you don't have any purchase records for/existing inventory that is in Items that is received but never sold, or sold but never received)

Answer 2

you can simply join with subquery

 Select Items.Name,Max(Items.Description) as Description ,
Max(ItemsStock.Quantity) as QuantityInStock,Max(ItemsStock.CurrentPrice)as CurrentPrice,V.VendorName
From ItemsSold
INNER Join Items On ItemsSold.ItemSoldID = Items.ItemID
INNER JOIN ItemsStock On ItemsSold.ItemSoldID = ItemsStock.ItemID
INNER JOIN  (
select max(PI.VendorID) VendorID,IR.ItemID
from ItemReceived IR
JOIN PurchaseInvoices PI on IR.PurchaseInvoiceID = PI.PurchaseInvoiceID
group by IR.ItemID
) Vendors ON Vendors.ItemID=Items.ItemID 
join Vendors v on v.VendorID=Vendors.VendorID
Group By Items.Name,V.VendorName