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70-465 | You need to recommend a solution to improve…

Question: 6

You need to recommend a solution to improve the performance of usp.UpdateInventory. The solution must minimize the amount of development effort.
What should you include in the recommendation?

A. A table variable
B. A common table expression
C. A subquery
D. A cursor

Answer: A

Explanation:

*Scenario: Database2 will contain a stored procedure named usp_UpdateInventory. Usp_UpdateInventory will manipulate a table that contains a self-join that has an unlimited number of hierarchies.
* A table variable can be very useful to store temporary data and return the data in the table format.
* Example: The following example uses a self-join to find the products that are supplied by more than one vendor.
Because this query involves a join of the ProductVendor table with itself, the ProductVendor table appears in two roles. To distinguish these roles, you must give the ProductVendor table two different aliases (pv1 and pv2) in the FROM clause. These aliases are used to qualify the column names in the rest of the query.
This is an example of the self-join Transact-SQL statement:
USE AdventureWorks2008R2;
GO
SELECT DISTINCT pv1.ProductID, pv1.VendorID
FROM Purchasing.ProductVendor pv1
INNER JOIN Purchasing.ProductVendor pv2
ON pv1.ProductID = pv2.ProductID
AND pv1.VendorID <> pv2.VendorID
ORDER BY pv1.ProductID

Incorrect:

Not B: Using a CTE offers the advantages of improved readability and ease in maintenance of complex queries. The query can be divided into separate, simple, logical building blocks. These simple blocks can then be used to build more complex, interim CTEs until the final result set is generated.

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