Lecture 1.ppt - Data Models Architecture This is the...

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Data Models & Architecture Dr. Alothaim Introduction to Database Systems Slide 1 This is the instructor s notes and student has to read the textbook for complete material.
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Outline 1. Database Management System 2. Purpose of Database Systems 3. Database Architecture 4. Data Models 5. Database Languages 6. Structured Query Language 7. Database Users 8. Database Administrator 9. Transaction Management 10. Storage Management 11. Overall System Structure 12. Application Architectures Dr. Alothaim Introduction to Database Systems Slide 2
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1. Database Management System (DBMS) Collection of interrelated data (database) Set of programs to access the data DBMS contains information about a particular enterprise DBMS provides an environment that is both convenient and efficient to use. Database Applications: Banking: all transactions Airlines: reservations, schedules Universities: registration, grades Sales: customers, products, purchases Manufacturing: production, inventory, orders, supply chain Human resources: employee records, salaries, tax deductions Databases touch all aspects of our lives Dr. Alothaim Introduction to Database Systems Slide 3
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2. Purpose of Database System In the early days, database applications were built on top of file systems Drawbacks of using file systems to store data: Data redundancy and inconsistency Multiple files, duplication of information in different files Difficulty in accessing data Need to write a new program to carry out each new task Data isolation — multiple files and formats Integrity problems Integrity constraints (e.g. account balance > 0) become part of program code Hard to add new constraints or change existing ones Dr. Alothaim Introduction to Database Systems Slide 4
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Purpose of Database Systems (Cont.) Drawbacks of using file systems (cont.) Atomicity of updates Failures may leave database in an inconsistent state with partial updates carried out E.g. transfer of funds from one account to another should either complete or not happen at all Concurrent access by multiple users Concurrent accesses needed for performance Uncontrolled concurrent accesses can lead to inconsistencies E.g. two people reading a balance and updating it at the same time Security problems Database systems offer solutions to all the above problems Dr. Alothaim Introduction to Database Systems Slide 5
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3. Database Architecture Internal level: describes how a record (e.g., customer) is stored. (Data structures) Conceptual level: describes data stored in database, and the relationships among the data. type customer = record NAME : string; ADDR : string; SEX : char; AGE : integer; end ; External level: describes only part of the database. Application programs hide details of data types. Example: Views can hide information (e.g., salary) for security purposes.
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