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Transcript of Databases
store and organize large amounts of data
People, Places, Objects
Example uses for a DB
A database is a collection of related data stored and organized in a manner so it can be retrieved as needed.
Parts of a Database
a category of information
all the information pertaining to one entry
search for information based on specific criteria:
temporary, cannot be saved or updated
Parts of a DB
Data from several different tables can be combined quickly using a relational database management system.
File management system
Allows the creation of a single database
Only one file accessed at a time
Database management system
Can access data from several different database tables at one time
Has the capability to use multiple tables and interrelate them
Includes helpful tools, such as a query language, programming-language facility, etc.
Types of Databases
Databases can contain multiple Tables, Forms, Queries, and Reports
Faster response time
Lower operating costs and storage requirements
Improved data integrity and better data management
Data integrity refers to the accuracy of data.
Data validation refers to the process of ensuring that data entered into the database matches the specifications.
Data security refers to protecting data against destruction and misuse.
Data Integrity and Security
The Evolution of Databases
HIERARCHICAL database management system: stores data in the form of a tree, which sets up a one-to-many relationship between data elements.
NETWORK database management system: relationship between data elements is usually either one-to-many or many-to-many.
E-commerce and E-business
Dynamic Web pages
Examples of Web Databases in use
In a hierarchical database (HDBMS), you begin with a strictly defined tree of data nodes. Each node can contain some identifying data, plus a set of subnodes of a specific child type. The number of subnodes can vary between sibling nodes at the same level, but the type of all "cousins" is identical. Figure 1 illustrates the relationships.
A RELATIONAL database consists of a set of tables, where each table consists a fixed collection of columns (also called fields). An indefinite number of rows (or records) occurs within each table. However, each row must have a unique primary key, which is a sort of name for that particular bundle of data. Figure 2 illustrates relational database structure (covering roughly the same data as the hierarchical example):
Object databases (ODBMSs) in some ways go back to the hierarchical model. Objects in an ODBMS -- much like objects in an object-oriented programming language -- are bundles of data and behaviors. In this sense, objects are similar to branch nodes of an HDBMS, which likewise contain a bundle of child nodes.
There are two unique features of object databases:
* Objects can be heterogeneous, and each contain a different collection of "owned" data
* Objects can contain some inherent "intelligence"
search for information based on specific criteria: permanent -editable - saved - updated