CP102 Databases (Chapter 11) Notes

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Computer Science
Igor Ivkovic

Databases - What is a database? o Definition: A database is a collection of information o Databases are typically stored as computer files o All tasks associated with databases such as creating, maintaining, accesing information in databases etc are referred to as data management, file management, or database management - How are these databases used? o Collect and store data  A database is defined as a collection of information/data, but the collection of data increases as more additional data is obtained.  Information/data can also be removed from a database when it is not needed and moved into an archive (Historical data not needed in the recent future, but can still be pulled out if inecessary) By removing unused data, you can keep the database lean and increase search speeds and conserve storage space. o Update data  One of the main database management activities is to keep the data up to date by entering current addresses etc.  Data entry errors can result in database inaccuracies. Organizations that maintain databases should be held liable for such errors o Organize and output data  Databases do not store data in any typical order. New data is attached to the end of the file. Data that is jumbled up is often not useful, and so it can be organized in variety of ways such as alphabetical, numerical order, size etc  Database output is easy to organize and rearrange in any given order without changing any of the physical data. Ex- A librarian can exact a list of patrons with overdue books organized by date, while at the same time a student can look for a list of books written a by a certain author. Different tasks, same database. o Distribute Data  Databases combine with other computerized technologies (ex. Mailmerge) to distribute information to customers, employees, government etc.  Ex. Your monthly electric bill is auto generated from the power company’s database. o Find Data  Databases make it easy to find information.  Ex. You can access the library database to access and check books available and shit. o Analyze Data  Databases include certain facts as raw data – names, dates, addresses etc. Analyzing such data using interpretive tools allows to extract information that would not necessarily be seen just by observing raw data  Techniques used for analyzing data include data mining and OLAP. - What is Data Mining? o Data mining refers to the process of analyzing existing database information to discover previously unknown information that can be very useful, such as relationships and patterns. o Data accessed by data mining and other analysis techniques are stores in a data warehouse  A data warehouse integrates data from varied sources o Data mining can be used to do predictive analysis  Predictive analysis is using current facts to make predictions about the future. - What is OLAP? o Online Analytical Processing o This is a data analysis technique which allows users to get answers to complex queries o TO analyze and mine complex data sets, decision makers can use an executive dashboard software which provides tools for visually displaying the query results - What is Big Data? o Big data refers to huge collections of data that are difficult to analyze using conventional database tools - Database Models o An unstructured file has a unique structure and different types of data whereas a structured file has uniform format to store data. o The underlying structure of a database is referred to as a database model - What is the simplest way to store ? o The simplest way to storing data is a flat file that consists of a single, two dimensional table of data/information. (Ex – iTunes playlist)  A field contains the smallest unit of meaningful information, also known as the basic bulding block for a structured database.  Each field has a unique field name  A field can be a variable-length field which expands to fit the data you enter up to a certain maximum OR a field can also be fixed- length field that contains a predetermined number of characters (bytes)  The template for a record is referred to as a record type. It contains names, but no data.  A record that contains data is referred to as a record occurrence, or simply just as a record. - A relationship is an associate between data that is stored in different record data types. o A cardinality refers to the number of associations that can exist between two record types.  One-to-many relationship  Many-to-many relationship  One-to-one relationship o The relationship between record types can be depicted graphically with an Entity-Relationship Diagram (ERD) - A hierarchal database allows one-to-one or one-to-many relationships - A network database uses a mesh-like structure for a many-to-many relationship. - What is a relational database? o A relational database stores data in a collection of related table o In a relational database, relatio
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