Microsoft® SQL Server® 2012 Bible

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Chapter 45: Indexing Strategies

45

FIGURE 45-10

The nonclustered index does not contain one or more columns that the query requests. To

solve the query, SQL Server must perform a bookmark lookup (the dashed line) from the

nonclustered index to the base table, which is a clustered index in this example. This illustra-

tion shows a single row. In reality it’s often hundreds or thousands of rows scattered

throughout the clustered index.

IX_WorkOrder_ProductID PK_WorkOrder_WorkOrderID

FIGURE 45-11

The query execution plan shows the bookmark lookup as an Index seek being joined with a

key lookup.

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