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Stairway to SQL Server Indexes: Step 9, Reading Query Plans Expand / Collapse
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Posted Monday, March 28, 2011 3:53 PM
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Comments posted to this topic are about the item Stairway to SQL Server Indexes: Step 9, Reading Query Plans
Post #1085228
Posted Wednesday, October 5, 2011 4:52 AM


SSCrazy Eights

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In the 'Viewing Parallel Streams' section you claim that both 'streams' are read in parallel. A hash join is a partially-blocking iterator: it consumes all rows from the build input to create the hash table, and then probes for matching rows one at a time from the probe input. This is clearly documented in Books Online - see Understanding Hash Joins.



Paul White
SQL Server MVP
SQLblog.com
@SQL_Kiwi
Post #1185771
Posted Friday, November 4, 2011 12:38 AM
Grasshopper

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Greetings,

As I have just read this part of articles. A question arise in my mind about figure 5. As my I understanding after reading untill part 9 is:

with query below
SELECT C.LastName, C.FirstName, C.MiddleName, C.Title, H.SalesOrderID, H.OrderDate
FROM Person.Contact C
JOIN Sales.SalesOrderHeader H ON H.ContactID = C.ContactID
WHERE Suffix is null
ORDER BY Title

I think the query plan should be still like figure 4 (not changing). This is because index IX_ContactID which added later does not give more advantage (lack field SalesOrderID to show for final output). How come with new index IX_ContactID and Clustered Index of table Contact, we can produce field SalesOrderID for final result?

Please give me enlightenment here .

Post #1200394
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