12 - Transaction Processing(LectureSession13 Chapters17...

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Transaction Processing (Lecture Session-13) Chapters 17 Fri, Feb 19, 2010 1 DLPD, BITS-Pilani.                Prepared  by Dr.R. Gururaj, Asst.Professor of CS
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Fri, Feb 19, 2010 DLPD, BITS-Pilani.                Prepared  by Dr.R. Gururaj, Asst.Professor of CS 2 Views in SQL A view in SQL is a single table that is derived from other tables. These other tables are known as base tables . A view does not necessarily exist in physical form, it can be considered as a virtual table. The tuples of base tables are actually stored in database. This limits the updates on views. In fact when a view is updated, the corresponding base tables are the structures which are to be updated. This makes update operations on views complex.
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Fri, Feb 19, 2010 DLPD, BITS-Pilani.                Prepared  by Dr.R. Gururaj, Asst.Professor of CS 3 Creating View CREATE VIEW EMP_DETAILS AS SELECT name, salary, dept name, age, dloc FROM EMPLOYEE, DEPARTMENT WHERE dno = dnumber; Whenever the view definition is executed, the new temporary table is generated with specified attributes from specified base tables. View definitions are stored in database, not the result of the view. From then onwards view can be seen as a table and queries can be posed on it. Ex. SELECT name, dname FROM EMP_DETAILS WHERE dno = 5; Here EMP_DETAILS is a view. Where this query is executed, first the view definition for EMP_DETAILS is executed and the select and where operation are performed on the temporary table.
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Fri, Feb 19, 2010 DLPD, BITS-Pilani.                Prepared  by Dr.R. Gururaj, Asst.Professor of CS 4 Note: A view is always upto date. Updates are generally not possible on views. Meant for querying only. Some times it is possible to store views for some duration. Those views are known as materialized views .
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Fri, Feb 19, 2010 DLPD, BITS-Pilani.                Prepared  by Dr.R. Gururaj, Asst.Professor of CS 5 Transaction Processing
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Fri, Feb 19, 2010 DLPD, BITS-Pilani.                Prepared  by Dr.R. Gururaj, Asst.Professor of CS 6 Introduction to transaction processing Concurrency control and Recovery Transaction states Desirable properties of a transaction Serialization Contents
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DLPD, BITS-Pilani.                Prepared  by Dr.R. Gururaj, Asst.Professor of CS 7 Multi-user systems : Multiple users access the database symultaneously (multi processing). Concurrency Transaction : A transaction is a collection of operations that perform a single logical operation or function in a database application. Each transaction is a unit of
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This note was uploaded on 03/14/2010 for the course CSE IS ZC332 taught by Professor Shailendrasshekhawat during the Summer '10 term at Birla Institute of Technology & Science.

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12 - Transaction Processing(LectureSession13 Chapters17...

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