18a_f09_ADO - Data Bases and ADO.NET Relational Databases...

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Data Bases and ADO.NET Relational Databases • Most data handling today done with relational databases – Logical representations of data that allow relationships among data to be considered without concern for the physical structure of the data – Composed of tables (like spreadsheets) – Lots of proprietary formats – Some database sources: • Microsoft SQL Server • Access • Oracle • Sybase – Microsoft ADO.NET can handle data from multiple locations (servers) stored in different formats
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ADO.NET • Based on Microsoft’s ActiveX Data Objects – Data stored and transferred in Extensible Markup Language (XML) – Allows simple access to database data in many formats • Easy-to-use classes represent tables, columns, rows inside relational databases • Introduces DataSet class representing a set of data from related tables encapsulated as a single unit preserving the integrity of the relationships between them – Basic types of database connections: • SQLClient for SQL Server • OleDb for all other database formats – Can be used to obtain/update data from sources such as Access, Oracle, Sybase, DB2, etc. • Many others supported Database Terminology • Each database file can hold multiple tables • A table : – Each row represents data for one item • Called a record – Each column used to store a different data element • Elements represented in columns are called fields Last Name First Name Phone --------------------------------------------- Smith John 777-1111 Jones Mary 777-2222 Records Fields
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Database Terminology, continued • Primary Key Field – Used to identify a record in a table – A field that contains unique data not duplicated in other records in the table • e.g., social security number for employees • Current Record – Anytime a table is open, one record is considered to be the current record • As we move from record to record in a table the current record changes Queries • A query retrieves information from a database • SQL (Structured Query Language ) is the standard for expressing queries – We won’t need to be experts in using it since Visual Studio .NET provides a “Query Builder” tool to construct SQL queries
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XML Data • Industry standard for storing and transferring data – Specs at: www.w3.org/XML • Most database formats store data in binary – Cannot be accessed by other systems or pass through firewalls • Data stored in XML is text – Identified by tags similar to HTML tags • Not predefined as in HTML • We can define our own XML tags to indicate their content – So very flexible for describing any kind of data • Use of XML allows programs to communicate even though they are written in different languages and run on different hardware Overview of XML • Machine-Readable and Human-Readable Data • Defines the Data Content and Structure • Allows Developer to Define his/her Own Tags and Attributes <employee> <name>Jake</name> <salary>25000</salary> <region>Ohio</region> </employee>
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This note was uploaded on 12/04/2009 for the course ER CS 360 taught by Professor Reckert during the Spring '09 term at Istanbul Technical University.

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18a_f09_ADO - Data Bases and ADO.NET Relational Databases...

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