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Accessing Databases using Ado

Accessing Databases using Ado.net. By Eric Vinokur. What we’re gonna do. Be introduced to technologies used for accessing databases Become familiar with some ADO.NET classes Look at what a database really is Understand how to use and manipulate data from databases

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Accessing Databases using Ado

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  1. Accessing Databases using Ado.net By Eric Vinokur

  2. What we’re gonna do • Be introduced to technologies used for accessing databases • Become familiar with some ADO.NET classes • Look at what a database really is • Understand how to use and manipulate data from databases • Be introduced to SQL Query Statements

  3. What is a database? • Location in a software that harbors large amounts of data • Information based • Physical Representation: • Collections of files with locations • LogicalRepresentation: • Records, fields, or tables • Software is needed to view databases in this way

  4. How to access a database • Client • Data Providers: • Microsoft Access • Microsoft SQL Server • Oracle • Open/Embedded Databases • Each provider must provide details for the methods that are used in the interface • ODBC and DBMS • Open Database Connectivity • Database Management System

  5. SQl server

  6. oracle

  7. Oracle

  8. SQL – Structured query language • SEQUEL • Designed by IBM in 1974 • Standardized language used for requesting and manipulating data • SQL Statements or Queries– SELECT, INSERT, UPDATE, and DELETE data in database tables

  9. Select Query • Select * From memberTable Order By LastNameAsc, FirstNameAsc; • Asterisk (*) selects all fields (columns) in database • Can replace * by field name(s) • Asc (ascending) returns in ascending order by LastName; duplicate last names ordered by first name • Retrieves all rows (records) • Where clause can be added to selectively identify rows Select PhoneNumber From memberTable Where FirstName = 'Gary' AND LastName = 'Jones';

  10. Sql statement – SQL Server

  11. Sql statement – Oracle

  12. ADO.Net • ActiveX Direct Objects • Addition to .NET Framework • Contains number of classes that can be used to retrieve, manipulate, and update data in databases. • Already exists in Visual Studio • Works in Disconnect (temp file) or Connect manner

  13. Main classes of ado.net • Connection • Command • DataReader • DataAdapter

  14. Using the classes

  15. Possible implementations • Close( ) • BeginDbTransaction( ) • ChangeDatabase( ) • CreateDbCommand( ) • OpenStateChange( )

  16. Datareader implementations

  17. Connection • Add using directive using System.Data.OleDb; • Instantiate an object of connection class • Send connection string that includes the actual database provider and the data source (name of the database) string sConnection; sConnection = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=member.mdb"; OleDbConnection dbConn; dbConn = new OleDbConnection(sConnection); dbConn.Open();

  18. Retrieving data with SQL stringsql; sql = "Select * From memberTable Order By LastNameAsc, " + "FirstNameAsc;"; // Note the two semicolons OleDbCommanddbCmd = newOleDbCommand(); dbCmd.CommandText = sql; // set command SQL string dbCmd.Connection = dbConn;// dbConn is connection object

  19. Retrieving data – continued • First call to dbReader.Read( ) retrieves first row • dbReader[0] refers to 1234 • dbReader[1] refers to “Rebecca” • dbReader["FirstName"] also refers to "Rebecca"

  20. Retrieving data – continued Member aMember; OleDbDataReaderdbReader; dbReader = dbCmd.ExecuteReader( ); // dbCmd—OleDbCommand object while (dbReader.Read( )) { // retrieve records 1-by-1... aMember = new Member(dbReader["FirstName"].ToString( ), dbReader["LastName"].ToString( )); this.listBox1.Items.Add(aMember); } dbReader.Close(); // Close the Reader object dbConn.Close(); // Close the Connection object

  21. Assignments are hand-written or typed in word

  22. Thank you • Except Nolter

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