Introduction to Database Changes and new experience make life delightful. Unanimous Data and Information How are data and information related? Next processing data stored on disk Step 1. The member data, including a photograph, is entered and stored on the hard disk. Step 2. The computer extracts the member data from disk. Step 3. The receipt is created and printed. Data is raw facts Information is data that is organized and meaningful receipt Computers process data into information Add, change, and delete data Create database Sort and retrieve data Create forms and reports Data and Information What is a database? Next Database software allows you to Collection of data organized so you can access, retrieve, and use it Database software also called database management system (DBMS) To create a database, designers must develop a conceptual design and a physical design Conceptual design: An abstract model of a database from the user or business perspective. Physical design: Layout that shows how a database is actually arranged on storage devices. Creating the Database Entity-relationship modeling: The process of designing a database by organizing data entities to be used and identifying the relationships among them. Entity-relationship (ER) diagram: Document that shows data entities and attributes and relationships among them. Entity classes: A grouping of entities of a given type. Instance: A particular entity within an entity class. Identifier: An attribute that identifies an entity instance. Relationships: The conceptual linking of entities in a database. The number of entities in a relationship is the degree of the relationship. Relationships between two items are common and are called binary relationships. There are three types of binary relationships: In a 1:1 (one-to-one) relationship, a single-entity instance of one type is related to a single-entity instance of another type. In a 1: M (one-to-many) relationship, a single-entity instance of one type is related to many-entity instance of another type. In a M:M (many-to-many) relationship, a single- entity instance of one type is related to many-entity of another type and vice versa. Entity- relationship diagram model Normalization A method for analyzing and reducing a relational database to its most streamlined form for minimum redundancy, maximum data integrity, and best processing performance Non-normalized relation Normalized relation Physical view: The plan for the actual, physical arrangement and location of data in the direct access storage devices (DASDs) of a database management system. Logical view: The users view of the data and the software programs that process that data in a database management system. The Hierarchy of Data What is a hierarchy? Next Database contains files, file contains records, record contains fields, field contains characters The Hierarchy of Data What is a field? Next Combination of one or more characters Smallest unit of data user accesses Field size defines the maximum number of characters a field can contain Field name uniquely identifies each field Data type specifies kind of data field contains Yes/No (also called Boolean)only the values Yes or No (or True or False) Hyperlink Web address that links to document or Web page Object (also called BLOB for binary large object)photograph, audio, video, or document created in other application such as word processing or spreadsheet The Hierarchy of Data What are common data types? Next Currency dollar and cent amounts or numbers containing decimal values Date month, day, year, and sometimes time Memo lengthy text entries Text (also called alphanumeric)letters, numbers, or special characters Numeric numbers onlyAutoNumber unique number automatically assigned to each new record The Hierarchy of Data What is a record? Next Group of related fields Key field, or primary key, uniquely identifies each record The Hierarchy of Data What is a data file? Next Collection of related records stored on disk key field recordsfields 22 Fifth Avenue P.O. Box Duluth Street Clark Street 1029 Wolf Avenue Address Auburn Clanton Prattville Montgomery City ALWeinbergJonah3928 ALMarcus4872 ALValesquezAdrian3376 ALMurrayShannon2928 ALVandenbergDonna2295 StateLast NameFirst NameMember ID Green Isolated datadata stored in separate files so it is difficult to access File Processing Versus Databases What is a file processing system? Next Data redundancy same fields stored in multiple files Each department or area within organization has own set of files May have weaknesses Records in one file may not relate to records in any other file File Processing Versus Databases What is the database approach? Next Many programs and users can share data in database Secures data so only authorized users can access certain data File Processing Versus Databases What are the strengths of the database approach? Next Reduced data redundancy Improved data integrity Shared data Shared data Easier access Reduced development time File Processing Versus Databases How do a database application and a file processing application differ in the way they store data? Next Database Management Systems What are popular database management systems (DBMSs)? Next Personal computer, midrange server, mainframe IBM CorporationDB2 Personal computer, midrange server, mainframe IBM CorporationInformix ServerMicrosoft CorporationSQL Server Personal computer, midrange server, PDA Sybase Inc.Sybase Personal computer, midrange server, mainframe, PDA Oracle CorporationOracle Personal computer, midrange server, mainframe Computer Associates International, Inc. Ingres Personal computer, server, PDAMicrosoft CorporationAccess Computer TypeManufacturerDatabase Database Management Systems What is a data dictionary? Next Contains data about each file in database and each field within those files Database Management Systems What is Structured Query Language (SQL)? Next Allows you to manage, update, and retrieve data Has special keywords and rules included in SQL statements SQL statement SQL statement results Database Management Systems What is a query? Next Request for specific data from a database Query language consists of simple, English-like statements that allow users to specify data to display, print, or store Step 1. Select the fields you want to display in the resulting query. Step 2. Assign a name to the query, so you can open it later. Step 3. View query on the screen. Database Management Systems What is a query by example (QBE)? Next Program retrieves records that match criteria entered in form fields Query by example screen criteria Query results Has a graphical user interface that assists users with retrieving data Database Management Systems What is a form? Next Window on screen that provides areas for entering or changing data in database Used to retrieve and maintain data in a database Form that sends data across network or Internet is called e-form, short for electronic form Database Management Systems What is a report generator? p. 532 Fig Next Allows user to design a report on screen, retrieve data into report design, then display or print reports Also called report writer What is a data model? p. 534 Fig Next Rules and standards that define how database organizes data Defines how users view organization of data The three most common data models are hierarchical, network, and relational. Other types of data models include multidimensional, object- relational, hypermedia, embedded, and virtual DATA MODELS FOR POPULAR DBMSs Data model Relational database What is a relational database? Next Stores data in tables that consist of rows and columns Each row has primary key Each column has unique name Stores data relationships Uses specialized terminology DATA TERMINOLOGY Relational database What is a relationship? Next Connection within data Hierarchical database model rigidly structures data into an inverted tree in which each record contains two elements, a single root or master field, often called a key, and a variable number of subordinate fields. The strongest advantage of the hierarchical database approach is the speed and efficiency with which it can be searched for data. The hierarchical model does have problems: Access to data in this model is predefined by the database administrator before the programs that access the data are written. Programmers must follow the hierarchy established by the data structure. Hierarchical Database Model Hierarchical Database model Data model that creates relationships among data in which subordinate records can be linked to more than one data element. Network Database Model Advantages and Disadvantages of Logical Data Models ModelAdvantagesDisadvantages Hierarchical databaseSearching is fast and efficient.Access to data is predefined by exclusively hierarchical relationships, predetermined by administrator. Limited search/query flexibility. Not all data are naturally hierarchical. NetworkMany more relationships can be defined. There is greater speed and efficiency than with relational database models. This is the most complicated database model to design, Implement, and maintain.Greater query flexibility than withhierarchical model, but less than with relational model. Relational databaseConceptual simplicity; there are no predefined relationships among data. High flexibility in ad-hoc querying. New data and records can be added easily. Processing efficiency and speed are lower. Data redundancy is common, requiring additional maintenance. Emerging Data Models Two emerging data models are the object-relational and hypermedia models Object-relational database model: Data model that adds new object storage capabilities to relational databases. Hypermedia database model: Data model that stores chunks of information in nodes that can contain data in a variety of media; users can branch to related data in any kind of relationship. Specialized Database Models Geographical information database: Data model that contains locational data for overlaying on maps or images. Knowledge database: Data model that can store decision rules that can be used for expert decision making. Small-footprint database: The subset of a larger database provided for field workers. Embedded database: A database built into devices or into applications; designed to be self-sufficient and to require little or no administration. Virtual database: A database that consists only of software; manages data that can physically reside anywhere on the network and in a variety of formats. What is an object-oriented database (OODB)? Next Advantages Often uses object query language (OQL) Stores data in objects Object is item that contains data, as well as actions that read or process data Can store more types of data Can access data faster What are examples of applications appropriate for an object-oriented database? Next Multimedia databases Store images, audio clips, and/or video clips Groupware databases Store documents such as schedules, calendars, manuals, memos, and reports Computer-aided design (CAD) databases Store data about engineering, architectural, and scientific designs Hypertext databases Contain text links to other documents Hypermedia databases Contain text, graphics, video, and sound Web databases Link to e-form on Web page