C1 basic concepts of database


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  • U can insert an email. Collection of data. ex.:
  • Not all people. Present data, ex. cgpa
  • DBMS; ex, atm
  • Example:An organization had records of employees in a table (entity type) called "Employees". In the table there would be attributes/columns such as First Name, Last Name, Job Name and Wage. The company also has data about the employee’s children in a separate table called "Children" with attributes such as First Name, Last Name, and date of birth. The Employee table represents a parent segment and the Children table represents a Child segment. These two segments form a hierarchy where an employee may have many children, but each child may only have one parent.
  • A record may be an owner in any number of sets, and a member in any number of setsBranches can be connected to multiple nodesThe network model is able to represent redundancy in data more efficiently than in the hierarchical model
  • C1 basic concepts of database

    1. 1. Basic Concepts of Database 1
    2. 2. Database definition• In general, a database is anything that stores data – Example, a phone book which store name & phone number• In computer, a database refers to – collection of organized data to be accessed, retrieved and used 2
    3. 3. Function of a database in general• Allow anyone to: – store (add) – delete (remove) – organize – use – present data 3
    4. 4. Example: data in Access database 4
    5. 5. What is a DBMS?• Database Management System is a software that store and manage database• It allows to: • create databases • insert, update and delete data • sort and query data • create forms and reports 5
    6. 6. Examples of DBMS• Microsoft Access, MySQL, PostgreSQL, SQL Server, Oracle, dBASE, Clipper and FoxPro• Examples of DBMS applications: Automated teller machine Computerized Library System Flight Reservation System Staff Information System Students System 6
    7. 7. DBMS Models• DBMS Model describe: – rules and standards on how database organize data – defines how users view organization of data• Common models include: (remember) – Hierarchical model – Network model – Object-oriented model – Relational model 7
    8. 8. Hierarchical Model• organizes data in a tree structure• all access to data starts at the top of the hierarchy and moves downward – for example, from customer to orders, vendor to purchases, etc• there is a hierarchy of parent and child data segments• support one to many relationship 8
    9. 9. Network Model• Similar like hierarchical model but – permit more than one parent per child – thus permit the modeling of many-to-many relationships in data• Organizes data using two fundamental constructs, called records and sets• Records contain fields , sets define one-to-many relationships between records: one owner, many members• Very flexible• Not widely use 9
    10. 10. Object Oriented Model• based on a collection of objects• an object contains: – values stored in instance variables within the object – bodies of code called methods that operate on the object• for example, consider an object representing a bank account – The object contains instance variables number and balance. – The object contains a method pay-interest which adds interest to the balance. – Under most data models, changing the interest rate entails changing code in application programs. – In the object-oriented model, this only entails a change within the pay- interest method.• Diverse structures• Can execute complex analytical and data manipulation operations to search and transform multimedia and other complex objects 10
    11. 11. Relational Model• Data is stored in two-dimensional tables (rows and columns)• Widely used• Example, Microsoft Access and MySQL 11
    12. 12. Data HierarchyDefinition- systematic organization of data, often in a hierarchicalformDatabase File Database File: Physical file stored in a storage media. Example: StudentDB.accdb Table Table: Contain information on a specific subject / topic. Example: Student, Courses Record: Contain information on single data item in a Record table. Example: information about a student. Also known as row in a table. Field Field: Contain a specific piece of information within a record. Example: Student Name, Student IC. Also known as column in a table. 12
    13. 13. Example of an Access tablerecords fields 13
    14. 14. Relational database• stores data in tables• tables are organized into columns, and each column stores one type of data• data for a single “instance” of a table is stored as a row 14
    15. 15. What is RDBMS?• RDBMS is a DBMS which manages a relational database – Example, Microsoft Access and MySQL• Data is structured in tables, records and fields• Each table consists of rows (records)• Each table row consists of one or more fields (columns)• RDBMS store the data into collection of tables, which might be related by common fields 15
    16. 16. Advantages of RDBMS• Minimum data redundancy• Data consistency - less likelihood of incorrect or incomplete data being stored or used• Integrated data – data is organized in logical relationship thus making it easy to relate data items• Data sharing – allows users from different department to share data• Data accessibility – allows users to access or retrieve in a flexible manner• Uniform security, privacy and integrity control – db administrator can establish control for accessing, updating and protecting the data 16
    17. 17. Categories of RDBMS• Personal database – Best in single-user environment (up to 10 users) – Example: Microsoft Access• Client/Server database – Support multiple users in a network environment – Run in a server, client can request data from the server & query, update & report locally – Example: SQL Server 17
    18. 18. Master table• Contains a primary key (must be unique as a password)• Normally is a table that lists the properties of things that have some permanence and used many times in other tables• Example customers, teachers, students and subjects offered 18
    19. 19. Transaction table• Records some kind of interaction or event between master tables• Transaction tables are typically used in posting operations or as lookup tables• Example, – In Student Information System, the actual classes taken by students are transactions because they record specific interactions between students and teachers – In an eCommerce software the shopping cart tables are all transaction tables, they record the purchase of items by customers 19
    20. 20. Primary Key• Field, or fields, which by itself, or together uniquely identify each row in a table• Used to match up records in different tables• Usually indexed• Help to define the relationships between tables 20
    21. 21. Primary Key• Requirement: must be unique and cannot be empty or null• Functions: • Used to associate data from multiple tables • Prevent duplicate record • Control the order of records • Faster to locate records• Possible to have 2 or more fields as primary key in a table –this is called composite key 21
    22. 22. Foreign Key• Same data field and type which is linked to a primary key in a corresponding table• Example: – In SalesTransaction table below, CustomerID would be the Foreign Key field – The Foreign Key is used to look up the CustomerID in the Customer table where the CustomerID is the primary keyCustomer table SalesTransaction tableCustomerID (PRIMARY KEY) SalesIDCustomerName SalesDate CustomerID (FOREIGN KEY) 22
    23. 23. Relationships• Relationships establishes the association between common fields in two tables• Common field links two tables to each other, thus ensuring connection between the data in the tables within the same database• REMEMBER: Access uses related tables - one table can find and use data in another table 23
    24. 24. What will we learn in this subject?• Access objects – Table, Query, Form, Report, Macro• Switchboard (is also a form)• SQL 24