By S. M. Deen (auth.)
Read or Download Principles and Practice of Database Systems PDF
Similar management information systems books
Outsourcing Management Information Systems
This e-book balances the optimistic results of outsourcing, that have made it a well-liked administration technique with the unfavourable to supply a extra inclusive determination; it explores possibility components that experience now not but been generally linked to this technique. It specializes in the conceptual "what", "why", and "where" features of outsourcing in addition to the methodological "how" features"
Design of Sustainable Product Life Cycles
Product existence cycle layout – producing sustainable product existence cycles explains the significance of a holistic long term making plans and administration method of attaining a greatest product gain over the total lifestyles cycle. The paradigm of pondering in product lifestyles cycles helps brands in shaping profitable items.
- Internet Management (Best Practices Series)
- IT Disaster Recovery Planning For Dummies
- 802.11 wireless network site surveying and installation
- Data simplification : taming information with open source tools
- Handbook of research on e-transformation and human resources management technologies: organizational outcomes and challenges
- Information Technology Entrepreneurship and Innovation
Extra info for Principles and Practice of Database Systems
Sample text
This happens because of the random nature of updates, which may result in having too many overflow records for some primary data area and too many underflow records in others. Thus the index becomes unbalanced, growing haphazardly in some directions, and shrinking in others. This leads to storage wastage and inefficiency, requiring periodic reorganisation of the index by a utility program. Such indexes require careful monitoring and maintenance, and therefore are not favoured in databases. The most widely used indexes are Balanced trees (B-trees) (Knuth, 1973; Comer, 1979) which we shall discuss below, along with two other recent ideas, one based on what is called a Hash tree (H-tree) and the other based on data-page splitting.
B-trees guarantee a balanced index, which is self-reorganising, and therefore extensively used in database implementation. It is also sometimes referred to as a dynamic indexing facility. 5 that all the internal identifiers can be accessed quickly in key order in both forward and backward directions. 3) so that the number of disc accesses is reduced to nearly 1 compared to (n-I) in the B-tree. We shall give below first the hash-tree technique and then an example. 50 Principles and Practice of Database Systems In this technique the key values are first compressed by an order-preserving compression algorithm to remove permanent gaps (that is, the value range that will never be filled) in such a way that the resultant compressed key values still retain the original key order.
4 Partially ordered pointers - see the text for explanation Pointers and Advanced Indexes 45 Overflow area. The entries in the brackets after each Si show: [Si (N, list of N internal identifiers Ii matching this Si)] . New records matching an existing Si can be inserted using the Overflow area if needed. 4(a), (b) and (c). However, the need to maintain the pointers always in the correct sequence in spite of insertions and deletions calls for a more elaborate organisation for the index. We shall discuss some of the relevant techniques in the next section.