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Data Entities, Attributes, and Keys (continued)
•Key:
–Field or set of fields in a record that is used to identify the record
•Primary key:
–Field or set of fields that uniquely identifies the record
The Database Approach
•Traditional approach to data management:
–Each distinct operational system used data files dedicated to that system
•Database approach to data management:
–Pool of related data is shared by multiple application programs
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The Database Approach (continued)
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The Database Approach (continued)
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Data Modeling and Database Characteristics
•When building a database, an organization must consider:
–Content:What data should be collected and at what cost?
–Access:What data should be provided to which users and when?
–Logical structure:How should data be arranged so that it makes sense to a given user?
–Physical organization:Where should data be physically located?
Data Center
•Climate-controlled building or set of buildings that:
–Houses database servers and the systems that deliver mission-critical information and services
•Traditional data centers:
–Consist of warehouses filled with row upon row of server racks and powerful cooling systems
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Data Modeling
•Building a database requires two types of designs:
–Logical design:
•Abstract model of how data should be structured and arranged to meet an organization’s information needs
–Physical design:
•Starts from the logical database design and fine-tunes it for performance and cost considerations
•Planned data redundancy:
–Done to improve system performance so that user reports or queries can be created more quickly
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Data Modeling (continued)
•Data model:
–Diagram of data entities and their relationships
•Enterprise data modeling:
–Starts by investigating the general data and information needs of the organization at the strategic level
•Entity-relationship (ER) diagrams:
–Data models that use basic graphical symbols to show the organization of and relationships between data
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The Relational Database Model
•Relational model:
–Describes data using a standard tabular format
–Each row of a table represents a data entity (record)
–Columns of the table represent attributes (fields)
–Domain:
•Allowable values for data attributes
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The Relational Database Model (continued)
•Manipulating data:
–Selecting:
•Eliminates rows according to certain criteria
–Projecting:
•Eliminates columns in a table
–Joining:
•Combines two or more tables
–Linking:
•Manipulating two or more tables that share at least one common data attribute
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The Relational Database Model (continued)
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The Relational Database Model (continued)
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Database Management Systems
•Creating and implementing the right database system:
–Ensures that the database will support both business activities and goals
•Capabilities and types of database systems vary considerably
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Overview of Database Types
•Flat file:
–Simple database program whose records have no relationship to one another
•Single user:
–Only one person can use the database at a time
–Examples: Access, FileMaker Pro, and InfoPath
•Multiple users:
–Allow dozens or hundreds of people to access the same database system at the same time
–Examples: Oracle, Sybase, and IBM
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Providing a User View
•Schema:
–Used to describe the entire database
–Can be part of the database or a separate schema file
•DBMS:
–Can reference a schema to find where to access the requested data in relation to another piece of data
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Creating and Modifying the Database
•Data definition language (DDL):
–Collection of instructions and commands used to define and describe data and relationships in a specific database
–Allows database’s creator to describe data and relationships that are to be contained in the schema
•Data dictionary:
–Detailed description of all the data used in the database
Creating and Modifying the Database (continued)
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Creating and Modifying the Database (continued)Fundamentals of Information Systems, Sixth Edition
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Storing and Retrieving Data
•When an application program needs data:
–It requests the data through the DBMS
•Concurrency control:
–Method of dealing with a situation in which two or more users or applications need to access the same record at the same time
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Storing and Retrieving Data (continued)Fundamentals of Information Systems, Sixth Edition
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Manipulating Data and Generating Reports
•Data manipulation language (DML):
–Commands that manipulate the data in a database
•Structured Query Language (SQL):
–Adopted by the American National Standards Institute (ANSI) as the standard query language for relational databases
•Once a database has been set up and loaded with data:
–It can produce reports, documents, and other outputs
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Database Administration
•DBA:
–Works with users to decide the content of the database
–Works with programmers as they build applications to ensure that their programs comply with database management system standards and conventions
•Data administrator:
–Responsible for defining and implementing consistent principles for a variety of data issues
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Popular Database Management Systems