Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Open Database Connectivity wikipedia , lookup
Entity–attribute–value model wikipedia , lookup
Microsoft Jet Database Engine wikipedia , lookup
Concurrency control wikipedia , lookup
Extensible Storage Engine wikipedia , lookup
Functional Database Model wikipedia , lookup
Relational model wikipedia , lookup
Database Management: Getting Data Together Chapter 14 Objectives • • • • • Describe the hierarchy of data Explain the differences between files and databases List the four database models Describe the concept of data integrity Describe the functions of a database management system • Describe the process of creating a database in general terms • Compare and contrast relational and object-oriented databases • Explain what a data warehouse is an how it differs from a database Contents • Computer Databases • Database Management Systems • The DBMS Process • Concurrency Control • Security • Backup and Recovery • Looking at the Data Computer Databases • Track information • Keep consistent standards • Allow higher productivity as a result of better information Hierarchy of Data • Field – Smallest meaningful unit of data – Group of one or more characters that has a specific meaning • Record – Set of fields containing all information known about one entity – Each record contains the same fields in the same sequence • File – Collection of related records Hierarchy of Data File Processing • File processing – Data redundancy • Database models reduce redundancy – Saves storage space – Saves update effort • Time • Accuracy Database Models • Database Types – Relational – Object-oriented – Hierarchical – Network • Each type structures, organizes and uses data differently RDBMS Relational Database Management System • Organizes data into related tables (files) • Table consists of rows and columns • Tables linked based upon a common field (key) RDBMS Key • Primary key – A field whose value uniquely identifies a record • Foreign key – Primary key of another table – Used as link to other table – May have duplicate values OODBMS Object-Oriented Database Management System • Manipulates object-oriented databases • Object – represents a real-world entity – Attributes / properties • Data about the entity – Methods / Actions • Operations that work the data OODBMS Object-Oriented Database Management System • Compared to RDBMS – More complex – Steeper learning curve – Skilled employees needed who earn high pay • Combined Object/relational DBMS – Relational database that incorporates some complex data types Data Integrity • Degree to which data is accurate and reliable • Integrity constraints – rules – Acceptable values for a field – Primary key values – Foreign keys • Integrity constraints must be enforced when data is entered or data is unreliable DBMS Database Management System Levels of software • Sophisticated – – – – Mainframe Expensive – tens of thousands of dollars Complex Planned and managed by computer professionals • Simple – PC – Inexpensive – few hundred dollars – User can set up and use the database DBMS Database Management System Basic functions • Create a database • Enter data • Modify the data as required • Retrieve information from the database DBMS Create a Database • Data Dictionary / Catalog – Stored data about the tables and fields within the database • Per table – Table name – Relationships • Per field – – – – Field name Data type Field size Validation rules DBMS Enter and Modify Data • Operations – Adding new data – Modifying data – Deleting data • Methods – User interacts directly with DBMS – Programs written by professional programmers access the data using special commands built into the DBMS DBMS Data Retrieval • Extracting the desired data from the database • Primary forms – Queries – Reports Query • Ask a question about the data • Present criteria that selects data from the database • Results in smaller portion of the database • Query Language – Prepare your query using English-like statements – Proprietary query language in DBMS Query SQL Structured Query Language Entered directly by user Included in programs QBE Query-by-Example Graphical interface to specify your criteria Report • Formatted presentation of data from the database • Normally printed • Designed using a report generator The DBMS Process Describe the data Review the data and edit until accurate Enter the data The DBMS Process The Plan… The Report… Concurrency Control • Databases are used concurrently by many users • Problem if several users attempt to update the same record at the same time • Record locking – First user requests record – Others are locked out for update Concurrency Control Security • Data is stored in a central location – Problem: unauthorized access is major concern – Benefit: easier to apply security measures • Features – User ID and password – Privileges assigned to each user • Read-only • Update Backup and Recovery • Why? – – – – Data can be accidentally damaged or destroyed Hardware can fail Forces of nature can cause physical damage Software or human errors can corrupt data • Backup – copy made periodically • Recovery – replaces the damaged database with the good backup Looking at the Data OLTP – Online Transaction Processing • Supports day-to-day database activities • Little support for data analysis Looking at the Data Data Warehouses • Databases designed to support ongoing operations • Data is captured from the db – Summary form – Scheduled basis – Period of time • May include data from external sources Looking at the Data Data Warehouses • Online Analytical Processing (OLAP) – Analyzes the data – Produces information for managers • Data mining – Statistical and artificial intelligence techniques – Look for unrecognized • • • • Patterns Relationships Correlations Trends – Helps managers make strategic business decisions