CS Second Half Notes

CS Second Half Notes - Databases Database Management...

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Unformatted text preview: Databases Database Management Systems (DBMS)- Software used for: o Database creation o Editing data o Sorting and retrieving data o Creating forms and reports Data vs. Information- Data = raw facts- Information = data that is organized and meaningful o Computers facilitate processing/converting data into information- Data Integrity o How correct is the data? o Garbage In Garbage Out (GIGO) Can’t create correct information if given incorrect data Qualities of Valuable Information- Accurate- Verifiable- Timely- Organized- Accessible- Useful- Cost-effective Why Databases?- Lots of Data o Need fast, efficient methods for access and maintenance- Multiple Users o Sharing data on one computer or across networks- Complex data organization o Complex relationships- Easy reports and queries Database Terminology- Field – basic fact o Ex. student name: Dex; phone number: 867 5309- Record – set of related fields o Student name and phone number are related- Table – set of recoded records o Students with phone numbers- Database – set of related tables File Processing vs. Databases- File processing o Separate sets of files o Records in one file may not relate to records in another o Disadvantages Data redundancy – same fields in separate files Isolated data – difficult to access data and relate it to other data- Advantages of Databases o Reduced data redundancy o Greater data integrity o Shared data o Easier access o Reduced development time Basic Database Operations- Find/Query o Request specific information from database- Display o Reports DBMSs come with generators User can specify the data layout and design for printing or display Database Models- Rules/Standards for organizing/representing data relationships- Popular data models: o Relational o Object-oriented o Object-relational o Multidimensional Relational Model- Stores data in tables o Rows – each row has a primary key o Columns – each column has a unique name- Stores data relationships o Connections within data between different tables Relational Databases- describe relationships among different data o collection of multiple tables with relationships to one another- Entity (Record) o Anything that can be identified by a fixed number of characteristics (attributes) o Example: Person FirstName Weight Height Gender Birthdate SSN, ect.- Attributes (Fields) o Have a name and associated value o Atomic data (indivisible/not decomposable) Example: address value: 1234 Sesame Street • Can’t separate number and street name- Structure o Specification of the information in an entity o Name: Person o Attrubute names and types of values (formals) FirstName Text width:30 Weight Number Gender Text width:1 Height Number Birthdate Date/Time MM/DD/YYYY SSN Number o Primary Key: SSN Relational Database Operations- Want to look up information- Users can request information from database- Performed on a table AND result is a table- Basic Operations o Select...
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This note was uploaded on 04/18/2008 for the course CS 110 taught by Professor Cettei during the Spring '08 term at UVA.

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CS Second Half Notes - Databases Database Management...

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