SQL Server Execution Plans - Red Gate Software

Chapter 7: Special Datatypes and Execution Plans
SELECT e.BusinessEntityID ,
p.LastName
FROM HumanResources.Employee AS e
JOIN Person.Person AS p
ON e.BusinessEntityId = p.BusinessEntityId
WHERE e.OrganizationNode.IsDescendantOf(@ManagerId) = 1
Listing 7.14
This query returns fourteen rows and runs in about 214ms with 48 reads on the
Person.Person table and three on the HumanResources.Employee table.
Figure 7.15 shows the execution plan.
Figure 7.15
As you can see, it's a very simple and clean plan. The optimizer is able to make use of
an index on the HIERARCHYID column, OrganizationNode, in order to perform an
Index Seek. The data then flows out to the Nested Loops operator, which retrieves data
as needed through a series of Clustered Index Seek commands on the Person.Person
table, which results in all the additional reads on that table. The interesting aspect of
this plan is the Seek Predicate of the Index Seek operation, as shown in the ToolTip in
Figure 7.16.
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