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Transcript
Relational Databases A database is an organized collection of data Some commercial products: MS Access, MS SQL Server, DB2, Oracle, mySQL, Sybase, db4o, Versant, IMS, Total, … Relational Databases introduced by E. F. Codd in 1969 A relational database is a collection of relations Relations A relational database comprises relations Common name for relation is table Structure: a table is a collection of rows and columns Structure resembles appearance of some spreadsheets everybody is familiar with tables this simplicity is one reason why relational databases have been very successful o in contrast IMS, Total, Versant are not so simple Small Example: database of one relation Employees Employee Id First Last Name Name 123 Joe Smith 333 Jim Jones 456 April Smith 842 Jenny Jones 777 Tom Lee Gender Male Male Female Female Male Verbalization We must be able to verbalize the information in a table. For the above Employee with ID … has a first name …, a last name …, and is of … gender Employee with ID 123 has a first name Joe, a last name Smith, and is of Male gender Employee with ID 333 has a first name Jim, a last name Jones, and is of Male gender Microsoft Access MS Access is a relational database system for workstations that run the Microsoft Windows operating system. typically used by individuals for data they use personally in some situations a single MS Access database may be used by a group of people or small department. MS Access databases are stored in a single file that has a file suffix of “.accdb” or “.mdb”. Databases created using MS Access 2007 and later have a file suffix “.accdb”, and databases created using MS Access 2003 or earlier have a file suffix “.mdb”. We will be using databases where the files have names ending in “.accdb”. You need to use MS Access 2007 or later to open the sample databases. MS Access Example: Library.accdb 3 tables: Member, Book, Loan Datasheet View vs Design View Viewing data Modifying/adding/deleting data