Ordered Indices - Ordered Indices 1. In order to allow fast...

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Ordered Indices 1. In order to allow fast random access, an index structure may be used. 2. A file may have several indices on different search keys. 3. If the file containing the records is sequentially ordered, the index whose search key specifies the sequential order of the file is the primary index , or clustering index . Note: The search key of a primary index is usually the primary key, but it is not necessarily so. 4. Indices whose search key specifies an order different from the sequential order of the file are called the secondary indices , or nonclustering indices . Primary Index o Dense and Sparse Indices o Multi-Level Indices o Index Update Secondary Indices Primary Index 1. Index-sequential files : Files are ordered sequentially on some search key, and a primary index is associated with it. Figure 11.1: Sequential file for deposit records. Dense and Sparse Indices 1. There are Two types of ordered indices: Dense Index:
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o An index record appears for every search key value in file. o This record contains search key value and a pointer to the actual record. Sparse Index: o Index records are created only for some of the records. o To locate a record, we find the index record with the largest search key value less than or equal to the search key value we are looking for. o
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This note was uploaded on 10/25/2010 for the course CMPN SEM4 taught by Professor Thakur during the Spring '07 term at University of Mumbai.

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Ordered Indices - Ordered Indices 1. In order to allow fast...

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