Is derived table executed once or three times?
- by AspOnMyNet
Every time you make use of a derived table, that query is going to be executed. When using a CTE, that result set is pulled back once and only once within a single query.
Does the quote suggest that the following query will cause derived table to be executed three times ( once for each aggregate function’s call ):
SELECT
AVG(OrdersPlaced),MAX(OrdersPlaced),MIN(OrdersPlaced)
FROM (
SELECT
v.VendorID,
v.[Name] AS VendorName,
COUNT(*) AS OrdersPlaced
FROM Purchasing.PurchaseOrderHeader AS poh
INNER JOIN Purchasing.Vendor AS v ON poh.VendorID = v.VendorID
GROUP BY v.VendorID, v.[Name]
) AS x
thanx
