TABLE OF CONTENTS Unit 1: Introduction to Database System 1.1 Introduction 1.2 Objectives 1.3 Traditional file oriented approach 1.4 Motivation for database approach 1.5 Database Basics 1.6 Three views of data 1.7 The three level architecture of dbms 1.7.1 External level or subschema 1.7.2 Conceptual level or conceptual schema 1.7.3 Internal level or physical schema 1.7.4 Mapping between different levels 1.8 Database management system facilities 1.8.1 Data definition language 1.8.2 Data manipulation language 1.9 Elements of a database management system 1.9.1 Dml precompiled 1.9.2 Ddl compiler 1.9.3 File manager 1.9.4 Database manager 1.9.5 Query processor 1.9.6 Database administrator 1.9.7 Data dictionary 1.10 Advantages and disadvantages of dbms 1.11 Self test 1.12 Summary Unit 2: Database Models 2.1 Introduction 2.2 Objectives 2.3 File management system 2.4 Entity-relationship (e-r) diagram 2.4.1 Intrdoction of ERD 2.4.2 Entity-relationship diagram 2.4.3 Generalization and aggregation 2.4.3.1 Aggregation 2.5 The hierarchical model 2.6 The network model 2.7 The relational model 2.8 Advantages and disadvantages of relational approach 2.9 An example of a relational model 2.10 Self test 1 2.11 Summary Unit 3: File Organisation For dbms 3.1 Introduction 3.2 Objectives 3.3 File organization 3.4 Sequential file organisation 3.4.1 Index-sequential file organization 3.4.1.1 Types of indexes 3.5 B-trees 3.5.1 Advantages of b-tree indexes 3.6 Direct file organization 3.7 Need for the multiple access path 3.8 Self test 3.9 Summary Unit 4: Representing Data Elements 4.1 Data elements and fields 4.2 Representing relational database elements 4.3 Records 4.4 Representing block and record addresses 4.5 Client-server systems 4.6 Logical and structured addresses 4.7 Record modifications 4.8 Index structures 4.9 Indexes on sequential files 4.10 Secondary indexes 4.11 B-trees 4.12 Hash tables 4.13 Self Test Unit 5: Relational Model 5.1 Introduction 5.2 Objectives 5.3 Concepts of a relational model 5.4 Formal definition of a relation 5.5 The codd commandments 5.6 Summary Unit 6: Normalization 6.1 Functional dependency 6.2 Normalization 6.2.1 First normal form 6.2.2 Second normal form 6.2.3 Third normal form 6.2.4 Boyce-codd normal form 6.2.5 Multi-valued dependency 6.2.6 Fifth normal form 6.3 Self test 6.4 Summary 2 Unit 7: Structured Query Language 7.1 Introduction of sql 7.2 Ddl statements 7.3 Dml statements 7.4 View definitions 7.5 Constraints and triggers 7.6 Keys and foreign keys 7.7 Constraints on attributes and tuples 7.8 Modification of constraints 7.9 Cursors 7.10 Dynamic sql Unit 8: Relational Algebra 8.1 Basics of relational algebra 8.2 Set operations on relations 8.3 Extended operators of relational algebra 8.4 Constraints on relations 8.5 Self test 8.6 Summary Unit 9: Management Considerations 9.1 Introduction 9.2 Objectives 9.3 Organisational resistance to dbms tools 9.4 Conversion from an old system to a new system 9.5 Evaluation of a dbms 9.6 Administration of a database management system 9.7 Self test 9.8 Summary Unit 10: Concurrency Control 10.1 Serial and serializability schedules 10.2 Conflict-serializability 10.3 Enforcing serializability by locks 10.4 Locking systems with several lock modes 10.5 Architecture for a locking scheduler 10.6 Managing hierarchies of database elements 10.7 Concurrency control by timestamps 10.8 Concurrency control by validation 10.9 Summary Unit 11: Transaction Management 11.1 Introduction of transaction management 11.2 Serializability and recoverability 11.3 View serializability 11.4 Resolving deadlocks 11.5 Distributed databases 11.6 Distributed commit 3 11.7 Distributed locking 11.8 Summary 4 UNIT 1 INTRODUCTION TO DATA BASE SYSTEM Unit 1: Introduction to Database System 1.1 Introduction 1.2 Objectives 1.3 Traditional file oriented approach 1.4 Motivation for database approach 1.5 Database basics 1.6 Three views of data 1.7 The three level architecture of dbms 1.7.1 External level or subschema 1.7.2 Conceptual level or conceptual schema 1.7.3 Internal level or physical schema 1.7.4 Mapping between different levels 1.8 Database management system facilities 1.8.1.1 Data definition language 1.8.1.2 Data manipulation language 1.8.1.3 Data query language 1.8.1.4 Data control language 1.8.1.5 Transaction control language 1.9 Elements of a database management system 1.9.1 Dml precompiled 1.9.2 Ddl compiler 1.9.3 File manager 1.9.4 Database manager 1.9.5 Query processor 1.9.6 Database administrator 1.9.7 Data dictionary 1.10 Advantages and disadvantages of dbms 1.11 Self test 1.12 Summary 1.1 INTRODUCTION Database Management is an important aspect of data processing. It involves, several data models evolving into different DBMS software packages. These packages demand certain knowledge in discipline and procedures to effectively use them in data processing applications. 5 We need to understand the relevance and scope of Database in the Data processing area. This we do by first understanding the properties and characteristics of data and the nature of data organization. Data structure can be defined as specification of data. Different data structures like array, stack, queue, tree and graph are used to implement data organization in main memory. Several strategies are used to support the organization of data in secondary memory. A database is a collection of related information stored in a manner that it is available to many users for different purposes. The content of a database is obtained by combining data from all the different sources in an organization. So that data are available to all users and redundant data can be eliminated or at least minimized. The DBMS helps create an environment in which end user have better access to more and better managed data than they did before the DBMS become the data management standard. A database can handle business inventory, accounting information in its files to prepare summaries, estimates, and other reports. There can be a database, which stores new paper articles, magazines, books, and comics. There is already a well-defined market for specific information for highly selected group of users on almost all subjects. The database management system is the major software component of a database system. Some commercially available DBMS are INGRES, ORACLE, and Sybase. A database management system, therefore, is a combination of hardware and software that can be used to set up and monitor a database, and can manage the updating and retrieval of database that has been stored in it. Most database management systems have the following facilities/capabilities: • Creating of a file, addition to data, deletion of data, modification of data; creation, addition and deletion of entire files. • Retrieving data collectively or selectively. • The data stored can be sorted or indexed at the user's discretion and direction. Various reports can be produced from the system. These may be either standardized report or that may be specifically generated according to specific user definition. Mathematical functions can be performed and the data stored in the database can be manipulated with these functions to perform the desired calculations. • To maintain data integrity and database use. • To create an environment for Data warehousing and Data mining. The DBMS interprets and processes users' requests to retrieve information from a database. The following figure shows that a DBMS serves as an interface in several forms. They may be keyed directly from a terminal, or coded as high-level language programs to be submitted for interactive or 6 batch processing. In most cases, a query request will have to penetrate several layers of software in the DBMS and operating system before the physical database can be accessed. 1.2 OBJECTIVES After going through this unit, you should be able, to Appreciate the limitations of the traditional approach to application system development; Give reasons why the database approach is now being increasingly adopted; Discuss different views of data; List the components of a database management system; Enumerate the feature/capabilities of a database management system; and List several advantages and disadvantages of DBMS. 1.3 TRADITIONAL FILE ORIENTED APPROACH The traditional file-oriented approach to information processing has for each application a separate master file and its own set of personal files. An organization needs flow of information across these applications also and this requires sharing of data, which is significantly lacking in the traditional approach. One major limitations of such a file-based approach is that the programs become dependent on the files and the files become dependent upon the programs. Disadvantages • Data Redundancy : The same piece of information may be stored in two or more files. For example, the particulars of an individual who may be a customer or client may be stored in two or more files. Some of this information may be changing, such as the address, the payment maid, etc. It is therefore quite possible that while the address in the master file for one application has been updated the address in the master file for another application may have not been.