Chapter 11 CS Introduction to Database Systems

Chapter 12 Databases and Database Users

Chapter 13 What is a Database? A collection of related data. It contains data specific to part of the real world, a miniworld. Consequently, it is a logically coherent collection of data. It is maintained for specific applications.

Chapter 14 Address Book Alan Arkin 200 Olive Street Ann Arbor, MI Birthday May 10th... Mary Ziegler 341 Einstein Drive Berkeley, CA Annivsy: July 12th

Chapter 15 September 1998

Chapter 16 Index on Cities Ann Arbor Berkeley Compton Allan Arkin John Doe Sue Smith Mary Ziegler John Law

Chapter 17 Stages in the Life of a Database Definition: specifying structures of tables and data to be stored. Construction: populating tables with data. Manipulation: queries, updates, deletes, etc.

Chapter 18 A DBMS (database management system) is a general-purpose software that enables users to define, construct and maintain various databases. ie. Oracle, Dbase IV However, databases have been implemented using a high-level language to define a collection of files. Using programs to access this files. This is traditional file processing.

Chapter 19 Fig 1.1

Chapter 110 A database system, which consists of a database together with DBMS software, is the complete environment in which a user operates.

Chapter 111 Fig 1.2

Chapter 112 Hypothetical situation: Smith and Brown are on probation and need approval from the instructor of each course that they scored a C or less. What are the names of these courses? Who are the instructors? Suggested changes to tables if these queries are frequent.

Chapter 113 What Problems could the University have regarding access to these tables?

Chapter 114 Solution “Virtual” tables or views allows the organization to selectively provide access to information while avoiding concurrency problems. Views also allow for the creation of dynamic summary views of information.

Chapter 115 fig 1.4

Chapter 116 Characteristics of the DBMS Approach Self-describing nature: Together with each database is stored a system catalog which is a separate entity containing information about each table in the database, types of each data item I.e. metadata!

Chapter 117 Insulation between programs & data: Consequence of using metadata. In traditional file processing the structure of the file is embedded in the access program, while with DBMS the structure of a file is defined separately in the system catalog, and is transparent to the access program. E.g.. in the University database if we added extra fields in GRADE_REPORT table, all programs that access this table would have to be rewritten! This is not true with a DBMS.

Chapter 118 Support of multiple views: A view may be a subset of the database, or may contain virtual data that is not explicitly stored, but instead it is derived. i.e. TotalHours in STUDENT_DUES. Sharing of data: A multi-user DBMS provides concurrency control software to allow multiple users to simultaneously access data. Such as bank accounts and airline reservations.

Chapter 119 Control of Redundancy: There are 3 main problems with redundancy: –duplication of effort –waste of space –possible inconsistency In the DBMS approach, redundancy is regulated by centralizing the data in one database, and providing various user groups with the views they need. However, controlled redundancy may sometimes be desirable

Chapter 120 Security & Authorization Mechanisms: Consequence of centralization. The DBA may restrict privileges (retrieve, update,etc) by either database, user or user’s role. Enforcing integrity constraints: A DBMS provides capabilities to enforce constraints or business rules I.e. each student must have a unique studentnumber. Providing Backup & Recovery: A DBMS provides facilities to recover from either software or hardware failures.

Chapter 121 DBMS Personnel Tool Developers DBMS Designers Database Administrator (DBA) System Analysts End Users –Casual- occasional high level use –Parametric- frequent canned transactions –Sophisticated - frequent high level use