EAK 362/2 MIS LECTURE 4 PART 2 Managing Databases

ENTITY: Any concrete or abstract object or event in the user’s world ATTRIBUTE: A characteristic of interest about an entity VALUE: A symbol or character string assigned to an entity instance to describe it RELATIONSHIP: Some connection or association between entities An organization collects information about Entities ­ any person, object, or event, however concrete or abstract. Attributes are the characteristics of interest about entities. Values of attributes represent the actual data pertaining to specific entities in the organization or its environment. Relationships may exist between entities and are usually represented by additional attributes. For example, recording the number of the organizational unit for which an employee works establishes a relationship between these two entities. ORGANIZATIONAL UNIT PERSON UNIT NUMBER : 2100 NAME: DEVELOPMENT DEPT. BUDGET: $391,000 PARENT UNIT: 2000 HEAD: P.I. Carr Entity Attribute Value Relationship LEVEL: EMPL POSITION TITLE: SECRETARY JOB CODE: 5210 ORG UNIT: 2100 SALARY: $31,400 EMPLOYEE NUMBER : NAME: R.F.CALLAGAN SEX: F BIRTHDATE: PRIMARY SKILL: 5210 SECONDARY SKILLS : 5520, 5220 o 2100 DEVELOPMENT DEPT P. I. Carr SUMMARY OF FIRST LECTURE

DATABASE There are four major database models, each of which has a different way of representing the relationships between entities. 1.HEIRARCHICAL DATABASE 2.NETWORK DATABASE 3.RELATIONAL DATABASE 4.OBJECT-ORIENTATED DATABASE an organized collection of data

1.Hierarchical Database Model What is the simplest database model? The simplest database model arranges record types as a hierarchy, or a hierarchical database. A record type in a hierarchical database is called a node or a segment. top node = root node parent node can have more than one child node child node can have only one parent node

Hierarchical Database Model What is the simplest database model? Hierarchical database model Department is the root node. It is also the parent node for the Employee and Job entities. The child nodes--Employee, Timecard, and Job--have only one parent node. Department is the parent node for Employee and Job. Employee is the parent node for Timecard. Notice that Employee is both a child node and a parent node. Department EmployeeJob Timecard

Hierarchical Database Model What is the simplest database model? In a hierarchical database, physical links are created between the stored records. effective for data that has simple relationships less effective for complex relationships and that require flexible data access

2. Network Database Model Which database model allows record types to have more than one parent? In a network database, related record types are referred to as a set. A set contains an owner which is similar to a parent record. also contains members (like child records) Only one-to-many relationships are allowed in the network database model. The network database model allows member records to have more than one owner. more flexibility than hierarchical

Network Database Model Which database model allows record types to have more than one parent? Network database model DepartmentJob Employee Timecard Job Employee The network database model allows a member to have more than one owner. Here the member Employee has two owners: Job and Department. An owner and its member or members are referred to as a “set.” Here the owner, Job, and the member, Employee, are a set. You could refer to the this section of the model as the “Employment set.” In a network database, records are classified as owners or members. Department and Job are owners in relation to Employee. Employee is an owner in relation to Timecard. Employee is a member under Department or Job. Timecard is a member under Employee.

3. Relational Database Model What if I need more flexibility to define relationships? A relational database is perceived by its users to be a collection of tables which are roughly equivalent to a collection of record types. rows of a table are called tuples (like records) columns of a table are called attributes (like fields) In a relational model, records are related to the data stored jointly in the fields of records in two files.

Relational Database Model What if I need more flexibility to define relationships? Relational database model The data for each record is stored in a table. A relational database for the Midtown General Hospital would have four tables: Employee, Timecard, Job, and Department. Data from the two tables can be combined by matching the data in two fields. For example, the data in the Employee and the Timecard tables can be joined by matching the data in the SocNum field.

4. Object-Oriented Database Model Do other data models exist? An object-oriented database model treats an entity as an object. object is defined by attributes object can be manipulated using methods objects with similar attributes are grouped in a class

Object-Oriented Database Model Do other data models exist? Object- oriented database model

Data management software helps you: create a collection of data enter and manipulate data format data into reports interact with data on the Web The software you select depends on: data model flexibility you require resources devoted to maintaining data Data Management Software

A database management system (DBMS) is application software that helps you manage the data in more than one file at a time. provides a way to create custom programs for data management tasks many provide an option for client/server operation Most users purchase a commercial DBMS package, such as Microsoft Access. Database Management Systems

Typical Capabilities of DBMS Create and maintain a database add, delete, revise records Extract and list records meeting certain criteria Make an inquiry (e.g. What were the total sales for 2002?) Sort records in ascending or descending order Provide on-screen forms for data input Generate formatted reports and charts

Querying the Database Query by example specify conditions e.g., list all students with marks > 80 The computer will quickly locate the record you seek Structured Query Language (SQL) standard method for accessing databases is a popular query language for microcomputers, mainframes, and supercomputers

Client/server Databases Traditional databases are located centrally Client/server technology permits data to reside at many locations on a network Users can query the database without regard for its physical location

Databases and the Internet Databases can be accessed via the Internet through a Web interface Often an interface can be developed for legacy databases The Common Gateway Interface (CGI) is used for this CGI is a standard for passing information between a Web server and other programs on the server

Interfacing to Databases Web browser CGI interface Database Server HTTP server

Example: Internet Search Engines Keywords you enter are converted to queries Queries are submitted to database Results are returned as HTML

Example: Library Catalogue Used to require dumb terminals for access Now accessed via the Internet Online Public Access Catalogue (OPAC) this uses telnet WebPac Web-based

A “data management environment” refers to the software or program that you use to design and manage data.” Regardless of the data management environment you use, many data management tasks remain the same. Data Management Tasks

Designing the File Structure Where do I begin? The key to an effective file or database is the initial design of its structure. Determine what data needs to be collected and stored. Two major inputs to this design Current system analysis Proposed system design

The second step is to organize the information into fields so that it can be used flexibly. Third step - decide on the data type for each field. After you specify the data type, you should decide on the format and valid range for each field. The field format provides a template for the way data is displayed on the screen. Many data management environments allow you to use a range check to specify what constitutes the range of valid entries and decrease errors. Designing the File Structure Where do I begin?

Designing the File Structure Where do I begin? Fourth - group the fields. Each group that you create becomes a record type. When you group fields into record types, you essentially make the choice between using a flat file and a database. Repetition of data is referred to as data redundancy. The process of analyzing data to create most efficient database structure is normalization.

Searching How do I find a particular record once it is entered? A database is like a vast warehouse of data. Data warehousing means collecting vast amounts of data, usually at least 10 GB. Data mining means combing though data to discover patterns and relationships important to decision making.

SUMMARY Database management is one of the main applications of computers DBMS allow databases to be built and manipulated without low-level programming Several types of database: relational and object-oriented most important today Many databases can be accessed using a Web browser