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First some information (followed by my question):
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From the book SQL Server 2005 Implementation and Maintenance
From page 154 under the section Implementing Clustered Indexes
It is a common misconception that a clustered index causes the data to be physically ordered in a table. That is not entirely correct: A clustered index causes the rows in a table as well as the data pages in the doubly linked list that stores all the table data to be ordered according to the clustering key. However, this ordering is still logical. The table rows can be stored on the physical disk platters all over the place. If a clustered index caused a physical ordering of data on the disk, it would create a prohibitive amount of disk activity.
From page 160 under Lesson Review Question 1
1. Which type of index physically orders the rows in a table
A. Unique index
B. Clustered Index
C. Nonclusted Index
D. Foreign Key
From page 853 (Answer)
A. Incorrect. -----
B. Correct. A clustered index causes the rows in the table to be physically ordered based on the index definition
C. Incorrect. -----
D. Incorrect. -----
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Now my question:
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How s it that on page 154, the book states that data being physically ordered is a misconception and that it would create a prohibitive amount of disk activity . Yet on page 853 under the answers to the test on page 160 on the same topic, the book describes clustered indexes as being physically ordered ? I have check the books errata listing and none of these pages are listed.
