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Các câu hỏi sau đây được dùng để củng cố thông tin quan trọng được trình bày trong bài học này. Các câu hỏi cũng có sẵn trên đĩa CD đồng nếu bạn muốn xem lại chúng dưới dạng điện tử. để thực hành làm thế nào để tương quan dữ liệu giữa các Profiler và hệ thống | 160 Chapter 4 Creating Indexes Lesson Review The following questions are intended to reinforce key information presented in this lesson. The questions are also available on the companion CD if you prefer to review them in electronic form. NOTE Answers Answers to these questions and explanations of why each answer choice is right or wrong are located in the Answers section at the end of the book. 1. Which type of index physically orders the rows in a table A. Unique index B. Clustered index C. Nonclustered index D. Foreign key 2. Which index option causes SQL Server to create an index with empty space on the leaf level of the index A. PAD_INDEX B. FILLFACTOR C. MAXDOP D. IGNORE_DUP_KEY Lesson 3 Creating Nonclustered Indexes 161 Lesson 3 Creating Nonclustered Indexes After you build your clustered index you can create nonclustered indexes on the table. In contrast with a clustered index a nonclustered index does not force a sort order on the data in a table. In addition you can create multiple nonclustered indexes to most efficiently return results based on the most common queries you execute against the table. In this lesson you will see how to create nonclustered indexes including how to build a covering index that can satisfy a query by itself. And you will learn the importance of balancing the number of indexes you create with the overhead needed to maintain them. After this lesson you will be able to Implement nonclustered indexes. Build a covering index. Balance index creation with maintenance requirements. Estimated lesson time 20 minutes Implementing a Nonclustered Index Because a nonclustered index does not impose a sort order on a table you can create as many as 249 nonclustered indexes on a single table. Nonclustered indexes just like clustered indexes create a B-tree structure. However unlike a clustered index in a nonclustered index the leaf level of the index contains a pointer to the data instead of the actual data. This pointer can reference one of .
