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Chapter 7 Basic Data Storage.pptx

  1. Chapter Seven Basic Data Storage 1
  2. Outcome of this chapter ⚫Describes databases and DBMS concepts, terminology, and architecture ⚫Describes the basic concepts necessary for a good understanding of databases design and implementation ⚫Describe the conceptual modeling techniques used in database systems ⚫Describes the relational data model, its integrity constraints and update operations, and the operations of the relational algebra 2
  3. Introduction to Database ⚫A database is an organized collection of data. ⚫It is the collection of schemas, tables, queries, reports, views and other objects. ⚫Database is a well-arranged and self-defining collection of data that is used to preserve data and metadata (Data about Data) and maintain data stability and integrity. 3
  4. Database Functionalities ⚫Data Storage Management ⚫Data Transformation and Presentation ⚫Security ⚫Multi-user Access Control ⚫Backup and Recovery ⚫Data Integrity ⚫Database Access Language ⚫Database Communication Interface. 4
  5. Applications of databases ⚫Banking: transactions ⚫Airlines: reservations, schedules ⚫Universities: registration, grades ⚫Sales: customers, products, purchases ⚫Online retailers: order tracking, customized recommendations ⚫Manufacturing: production, inventory, orders, supply chain ⚫Human resources: employee records, salaries, tax deductions 5
  6. Advantages & Disadvantages of DB Advantages: ⚫High data quality, integrity, and consistency ⚫Reduced data redundancy and application maintenance ⚫Easy access and sharing ⚫Scalable ⚫Improved security ⚫Specialized and productive management tool Major disadvantages: ⚫ Increased complexity ⚫Greater impact of failure 6
  7. Relational Database ⚫A relational database (RDB) is a collective set of multiple data sets organized by tables, records and columns. ⚫RDBs also establish a well-defined relationship between database tables. ⚫In simplest terms, a relational database is one that presents information in tables with rows and columns showing relation between them. 7
  8. Database Management System ⚫All the database design and data manipulation tasks are carried by a Database Management System (DBMS). ⚫It is computer software designed for the purpose of managing databases based on a variety of data models. 8
  9. Schema and Instance Schema : logical structure of the database is called Schema. Instance : The actual content of the database at a particular point in time is called an Instance. 9
  10. Database table properties ⚫Unique table name. ⚫All values in a row describe the one instance. ⚫All values in a column are of the same kind. ⚫Each row is distinct. ⚫A cell of the table holds a single value. ⚫Each column has a unique name. ⚫There is no ordering in rows. ⚫NULL value can also be stored in tables. 10
  11. A simple Database Table In a database, data are organized in relations (tables) which may be linked by some constraints. Columns contain what information is needed to be stored and Rows contain each record. For example, in a university database, there can be tables to store information about courses, instructors, student, section etc. Columns are called fields and each row contains record which stores value for each field. Here, ID, name, dept_name and salary are the fields to store and {2222, Einstein, Physics, 95000} is a record. 11
  12. Data Model ⚫A detailed model that captures overall structure of organizational data while being independent of any implementation considerations. ⚫Data modeling involves examining the data objects in a system and identifying the relationship between these objects. ⚫There are different ways of model a database. They are: ⚫ Relational model ⚫ Entity-Relationship data model (mainly for database design) ⚫ Object-based data models (Object-oriented and Object- relational) ⚫ Semi structured data model (XML) 12
  13. Entity, Attributes and Relationships ⚫Entity: An entity is an object that exists and is distinguishable from other objects. It is the primary task to determine all the entities and their attributes while modeling a database. Entities are denoted using rectangle. Example: specific person, company, event, plant. ⚫Attribute: An entity is represented by a set of attributes that is descriptive properties possessed by an entity. Attributes are denoted using elliptical shape. Example: instructor = (ID, name, street, city, salary), course= (course_id, title, credits) ⚫Relationship: A relationship is an association among several entities. Entity relationships are denoted using rhombus shape. Example: students are enrolled in courses. Instructor teaches courses. 13
  14. Entities & their Attributes with Relationship in a University Database 14
  15. Primary key ⚫ A primary key is a candidate key and a single field that is most appropriate to be the main reference key for the table. ⚫ The primary key must contain unique values, must never be null and uniquely identify each record in the table. ⚫ For example, in a Students table, we can see that, using only {StudentID} it is possible to identify each record distinctly. So, this is the primary key for the table. 15
  16. Foreign key ⚫ A foreign key is generally a primary key from one table that appears as a field in another table to establish a relation between the first and second table. ⚫ For example, consider the relationship between Students and Courses. Student information is stores in Students table and course information is stored in Courses table. From these two tables how to show that which student have which courses? This is done using a foreign key field {courseId} in the Students table, which will contain the values of {courseId} field of Courses table. 16
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  18. Question ⚫ What is database? Why do we use database? What are the advantage and disadvantage of database? ⚫ What is DBMS? What is schema and instance? What are the properties of database table? What is Field and Record? ⚫ What is a relational database? Find the tables necessary for a Library Management System/ Hospital Management System. ⚫ What is a data model? What are entity, attribute and Relationship? Discuss with example. ⚫ Find all the entities of an online bookshop management database. Find out all the attributes for each entity. ⚫ Find all the entities of a Shopping Store management database. Find out all the attributes for each entity. ⚫ What is Primary key? Describe with example. ⚫ What is Foreign Key? Why do we use Foreign Key in a database? Explain with example. ⚫ For an online book shop database, identify the Primary Key and Foreign Key in Customers and Orders table. 18
  19. Thank You 19