Question

I have a view that I can’t seem to fully tune, so I tried converting it to a proc, moving one of my WHERE conditions that I use when querying into a parameter and using the parameter in my derived tables.

View

CREATE VIEW myView
AS
SELECT     i.ItemCode
           , s.StoreID
           , ISNULL(SUM(s.TotalSales)) AS Sales
FROM       Item i
LEFT JOIN  Balance b ON i.ItemCode = b.ItemCode
LEFT JOIN  (SELECT    SUM(Quantity)
                      , StoreID
                      , ItemCode
                      , Date
            FROM      Sales
            GROUP BY  StoreID
                      , ItemCode
                      , Date) AS s    ON i.ItemCode = s.ItemCode
                                      AND s.Data >= COALESCE(b.Date, '01-01-1900)
JOIN
GROUP BY    i.ItemCode
            , s.StoreID

Stored Proc

CREATE PROCEDURE myProc(@StoreID INT)
AS
SELECT     i.ItemCode
           , s.StoreID
           , ISNULL(SUM(s.TotalSales)) AS Sales
FROM       Item i
LEFT JOIN  Balance b ON i.ItemCode = b.ItemCode
LEFT JOIN  (SELECT    SUM(Quantity)
                      , StoreID
                      , ItemCode
                      , Date
            FROM      Sales
            WHERE     StoreID = @StoreID
            GROUP BY  StoreID
                      , ItemCode
                      , Date) AS s    ON i.ItemCode = s.ItemCode
                                      AND s.Data >= COALESCE(b.Date, '01-01-1900)
JOIN
GROUP BY    i.ItemCode
            , s.StoreID

EXEC myProc(100) is much faster than SELECT * FROM myView WHERE StoreID = 100.
Should this be the case?

Note: I know this code may not make perfect sense or run — I’ve tried to simplify it by removing some other JOINs. The only substantial difference in the real code is moving the WHERE into the derived table, which I’ve done here.

Shouldn’t the view take my WHERE into account when performing the derived table queries and be just as fast as the proc?

Thanks for any help!

Answer 1

The two queries are quite different. The difference is very subtle, but this is the line:

        WHERE     StoreID = @StoreID

The view calculates all the data for all the stores. It then filters the results for a particular store.

The stored procedure version is only looking at the particular store; it can even make efficient use of an index on StoreId if there is one.