Relational Database Systems Bartosz Zagorowicz

Flat Databases  Originally databases were flat.  All information was stored in a long text file, called a tab delimited file.  Each entry in the TDF is separated by a special character, such as a vertical bar ( | ).

Problem  Difficult to search for specific information.  Difficult to create reports that include only certain fields.  Have to search through the entire file to find information

Relational Database  Invented in 1970 by IBM researcher, E.F. Codd.  They use tables to store information.  Standard fields and records are represented as columns (fields) and rows (records) in a table.

Advantages  Allow you to easily find specific information.  Ability to sort based on any field.

Advantages  Ability to generate reports that contain only certain fields from each record.  You can quickly compare ages and salaries because of this arrangement.

Practical Application  How do you manage customer orders?  How many orders did John Smith make last week, month, year? What is the most popular product? What points during they year are sales the highest?  Excel spread sheet?

“Relational”  Typical databases have anywhere from 10 to 10,000 tables.  It builds new tables out of required information from existing tables.  It uses the relationship of similar data to increase the speed and versatility of the database.

“Relational”  The database uses mathematical relations.  It builds new tables out of required information from existing tables.  Each table contains columns that other tables can use to gather information from that table.

Size, Speed and Scalability  By storing this information in another table, the database can create a single small table with the locations that can then be used for a variety of purposes by other tables in the database.  Large websites such as Amazon.com contain hundreds of thousands of tables, used together to quickly find exact information

Relational Model Components  Structures – Well defined objects (tables, views, indexes). Structures and their data can only be manipulated by operations.  Operation – Clearly defined actions that allow users to manipulate data. Operations must adhere to integrity rules  Integrity Rules – Laws that govern which operations are allowed on the data structures of a database.

SQL  Relational databases are created using a special computer language, structured query language (SQL.)  SQL is the industry standard language supported by almost every relational database management system on the market

MySQL  RDBMS – Relational Database Management System  Popular choice of database for use in web applications used by websites such as Flickr, Youtube, Wikipedia, Google and Facebook.

Relational Database Management Systems  A database management system based on the relational model.  DBMS in which data is stored in tables and the relationships among the data are also stored in tables.

Query Example  SELECT * FROM Book Where price > ORDER BY title;  SELECT name, e_mail FROM addr_book WHERE company = microsoft

Amazon.com  SELECT * FROM electronics Where price < 400 ORDER BY price;

Relational Database Management Systems  The data can be accessed or reassembled in many different ways without having to change the table form.  Oracle, SQL Server, MySQL, Sybase, DB2, TeraData are examples of database systems.

MySQL  Tables,  Structures  Associations  Dependencies

Benefits of Relational Databases  Dynamic Views (join, simplify data), hides complexity  SQL is easy and human readable language  Provides search options  Excellent security (access permissions)

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