An Overview of Database Management Systems

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Overview of Database Management Systems

• Goals:
– DBMS basic concepts – Introduce underlying managerial issues – Prepare for discussion of uses of DBMS, such as OLAP and database mining

misnotes-dbms-19980121.ppt

Steven O. Kimbrough

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Overview of Database Management • What is a database system? – Acomputerized record-keeping system

• Record?
– Think of it as a row in a table, consisting of fields of data – Note: Role of metaphors

• System?
– A general software module that provides all sorts of services: – Create new files and add them to the database – Insert new data into an existing file – Retrieve data from existing files – Update (change) data in existing files – Delete data in existing files – Delete (remove) existing files from the database – And much else: system management features, security, integrity, etc.

misnotes-dbms-19980121.ppt

Steven O. Kimbrough

2

Overview of Database Management • Important and fundamental distinctions – System software vs application software – Logical vs physical » See MIS Notes, chapter 1

• System software, e.g.,
– – – – Operating system Language compilers Communications DBMS

• Idea: everybody needs it, so write it once and standardly for all – Reading/writing files (OS) – Storing/retrieving records (DBMS)

misnotes-dbms-19980121.ppt

Steven O. Kimbrough

3

Overview of Database Management • Where do database systems come from? – Commercial software vendors » Oracle, DB2, RDB, Ingres, Focus, etc. for mainframes » For Unix, Oracle, Ingres, Informix, etc. » Macs: Mainly Oracle » PCs: Access, Paradox, Oracle, etc.

• Is there more than one kind? Why?
– Yes: flat file systems, network systems, hierarchical systems, relational systems, object-oriented systems – And different brands for each type – Why? History, needs and requirements

• Is there a standard? Yes, 2 really
– Relational DBMS – SQL as the access language » DDL, DML, etc. » Note: Can have SQL w/o relational and relational w/o SQL – Note: Access is relational & has SQL access misnotes-dbms-19980121.ppt Steven O. Kimbrough

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Overview of Database Management • Who uses database systems? – – – – Everyone, high, middle, and low Pervasive in business and commerce Difficult to overestimate importance Quite possible to earn your way through school doing database work

• Are databases here to stay? Are they stable?
– Here to stay? Absolutely! – Stable? Yes, but... » Relational DBMS with SQL: commercial de facto standard; client-server uses » Object-oriented DBMS: thought to be the next big thing • • • A few years away Specialized uses SQL will stay---probably

misnotes-dbms-19980121.ppt

Steven O. Kimbrough

5

More Comments on Database and Information Systems Generallly • Important concepts/themes • Persistence – Why we need data bases

• Metaphors and computing generally and database specifically – Relational model, relational databases: » Tables, tables, tables

• Indirection
– e.g. external, conceptual, internal views of database

misnotes-dbms-19980121.ppt

Steven O. Kimbrough

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Overview of Database Management
• • • Why database? Alternatives are unattractive Positive reasons for DBMSs • • • • • • • Data independence Reduction of redundancy Avoidance of inconsistency Enforcement of standards Security Integrity Use of markets

misnotes-dbms-19980121.ppt

Steven O. Kimbrough

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Database Architecture
• • • • These comments apply broadly to all types of DBMSs ...but, will focus on SQL, "big guys" systems ANSI/SPARC (broadly accepted) framework Three levels: • External • Conceptual • Internal "Relational" refers to how the data appears to users, so to the external and conceptual levels – How it appears (as tables) and – How you operate on it – Recall: metaphors



misnotes-dbms-19980121.ppt

Steven O. Kimbrough

8

The External Level
• The individual user level (application programmer, someone interacting online with the...
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