SQL Server Execution Plans - Red Gate Software

Chapter 5: Controlling Execution Plans with Hints
LOOP|MERGE|HASH JOIN
These hint methods make all the join operations in a particular query use the method
supplied by the hint. However, note that, if we also apply a join hint (covered later) to
a specific join, then the more granular join hint takes precedence over the general
query hint.
In this situation, we've found that our system is suffering from poor disk I/O, so we need
to reduce the number of scans and reads that our queries generate. By collecting data
from Profiler and Performance Monitor, we identify the query in Listing 5.7 as one that
needs some tuning.
SELECT pm.Name ,
pm.CatalogDescription ,
p.Name AS ProductName ,
i.Diagram
FROM Production.ProductModel AS pm
LEFT JOIN Production.Product AS p
ON pm.ProductModelID = p.ProductModelID
LEFT JOIN Production.ProductModelIllustration AS pmi
ON p.ProductModelID = pmi.ProductModelID
LEFT JOIN Production.Illustration AS i
ON pmi.IllustrationID = i.IllustrationID
WHERE pm.Name LIKE '%Mountain%'
ORDER BY pm.Name;
Listing 5.7
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