Textbook Notes (363,261)
Canada (158,278)
CP102 (83)

CH11 Behind the Scenes.docx

3 Pages
Unlock Document

Wilfrid Laurier University
Computer Science
Mark Petrick

CH11 Behind the Scenes: Databases and Information Systems  Database: collection of related data that can be easily stored, sorted, organized, and queried o Most practical when there’s complex data that needs to be organized or shared  Problem with lists: data redundancy and inconsistency, how to handle incomplete data, organization can be labour intensive, incorrect info can be entered Database building blocks  Without them, you couldn’t store and retrieve large quantities of info easily  3 main advantages: enable information sharing, promote data integrity, allow flexible use of data o provides data centralization, increases efficiency, reduces errors when data is entered/updated o data integrity: data contained in database is accurate and reliable o data centralization: ensures integrity o makes information dissemination tasks easier o can manage larger amounts of data and process that data more efficiently  disadvantages: time consuming, expensive to set up, privacy concerns  3 main components: fields, records, tables (or files)  field: database stores each category of information here o data type (field type): when fields are created in the database, user assigns this. Common types include:  text field: can hold any combination of alphanumeric data but is most often used to hold words  numeric field stores numbers, values can be used to perform calculations  computational field: stores the contents of a calculation generated with a formula in the numeric field  date/time field: holds data such as birthdays and due dates  memo field: text field but can hold long pieces of text  object field: holds items such as pictures, video clips or documents  hyperlink field stores hyperlinks to web pages o field size defines the maximum number of characters or numbers that a field can hold  record: group of related fields  table: group of related records  fields can have the same values in the same table  to keep records distinct, each record must have one field that has a value unique to that record o unique field is called primary key or a key field. Makes it impossible to duplicate records Database Types  relational database organizes data in table format by logically group similar data into a relation o tables are logically linked to each other by including their primary keys in other tables with related information o contain structured (analytical) data  object-oriented database stores data in objects rather than in tables o store instructions for doing computations in the same places as they store data, they can usually process requests for info faster than relationship databases can o contain unstructured data- nontraditional data such as audio clips, video clips, pictures; known as binary large object (BLOB) because it’s encoded in binary form o much more complex data than relational databases o use a query language to access and manage data  query language: specially designed computer language that is used to manipulate data in or extract data from a database  many object-oriented databases use Object Query Language (OQL) which is similar to Structured Query Language (SQL)  multidimensional database stores data in more than two dimension, ex eBay o organizes information in cube format o advantages: easily customized to provide info to a variety of users, process data much faster than relational databases o each data cube has a measure attribute which is the main type of data that the cube is tracking o other elements of the cube are known as feature attributes, which all describe the measure attribute in some meaningful way Database Management Systems: Basic Operations  database management system (DBMS) creates and manages databases  specially designed application software that interacts with other applications for 4 main operations: creating databases and entering data; viewing and sorting data; querying (extracting) data; outputting data  Creating databases and entering data o First create data description, referred to as the data dictionary or database schema o Each field should describe a unique piece of data and should never combine 2 separate pieces of data o Metadata: data that describes other data, integral part of data dictionary  Inputting Data o Import from spreadsheets, documents o Input form speeds manual data entry, provides a view of the data fields to be filled with appropriate labels to assist database users in populating the database  Data Validation o Validation: process of ensuring that data entered into the database is correct and complete o Validation rule is set up to alert the user if there’s a mistake, part of the data dictionary o Range check ensures that the data entered falls within a certain range of numbers o Field constraint: property that must be satisfied for an entry to be accepted into the field o Completeness check: ensures all fields defined as required have data entered into them o Consistency check: compares the values of data in two or more fields to see if these values are reasonable  Extracting or Querying Data o Query: question or inquiry o Database query: question you ask the database so that it provides you with the records you wish to view  Use SQL query language o Simple query wizard takes the criteria you specify and creates the appropriate SQL commands  Outputting Data o Most common form of output: viewable electronic report o Can export data to other applications Relational Database Operations  Relationship: link between tables that defines how the data is related  Both tables must have a common field, usually involves primary keys of a table  One-to-one: indicates that for each record in a table there is only one corresponding record in a related table  O
More Less

Related notes for CP102

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.