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Understanding Databases and Data Representation in CS360 Windows Programming

This guide explores fundamental concepts of databases and data representation in the CS360 Windows Programming course. It covers one-to-many relationships, the use of primary and foreign keys, and how to create views in SQL. It includes practical examples of querying data using views and inner joins, especially in the context of MySQL connections using C#. The guide also touches upon error handling techniques and best practices for managing database connections within your programming projects.

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Understanding Databases and Data Representation in CS360 Windows Programming

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  1. Databases and Data Representation CS360 Windows Programming

  2. Relationships • Relation: one-to-many LectID Name Course Students LectID Building Room OfficeID Primary key Foreign key CS360 Windows Programming

  3. Database Views • CREATE VIEW StrainOffices AS SELECT OfficeID, LectID, Room FROM Offices WHERE Building = ‘Strain’ LectID Building Room OfficeID LectID Room OfficeID CS360 Windows Programming

  4. Database Views • Views do not store data – they are “virtual” tables • If we query a view, tuples are obtained from the base table so that the query can be answered • SELECT OfficeID, RoomFROM StrainOfficesWHERE LectID = 1 LectID Room OfficeID Room OfficeID CS360 Windows Programming

  5. Database Views • We can rename the columns in the view if we want • CREATE VIEW StrainOffices(OId, Lid, RoomNum) AS SELECT OfficeID, LectID, Room FROM Offices WHERE Building = ‘Strain’ LId RoomNum OId CS360 Windows Programming

  6. Database Joins LectID Name Course Students LectID Building Room OfficeID Primary key Foreign key CS360 Windows Programming

  7. Joins • SELECT * FROM Lectures INNER JOIN Offices ON Lecturers.LectID = Offices.LectID ORDER BY Offices.LectID CS360 Windows Programming

  8. Your Turn • SELECT Name FROM Lecturers INNER JOIN Offices ON Lecturers.LectID = Office.LectIDINNER JOIN Advisees ON Lecturers.LectID = Advisees.AdvIDWHERE Building = ‘Strain’ AND Name = ‘Harry’ AdvID LectID Name LectID Name Course Students OfficeID LectID Building Room CS360 Windows Programming

  9. Connecting to MySQL • C# can connect to MySQL • Need to download a .NET connector • http://dev.mysql.com/downloads/connector/net/1.0.html • Need the MySql.Data.dll • I’ve placed it in CS360 Pub under MySQL Connector\bin\.NET 1.1 CS360 Windows Programming

  10. Connecting to MySQL CS360 Windows Programming

  11. Connecting to MySQL using MySql.Data.MySqlClient; string connStr = "server=cs445.cs.pacificu.edu; user id=shereen; password=abc123; database=shereen;"; MySqlConnection conn = null; MySqlDataAdapter da = null; MySqlDataReader reader = null; MySqlCommand cmd = null; CS360 Windows Programming

  12. Connecting to MySQL try { conn = new MySqlConnection(connStr); conn.Open(); cmd = new MySqlCommand("SELECT * FROM pet", conn); reader = cmd.ExecuteReader(); lb2.Text = ""; while (reader.Read()) { lb2.Text = lb2.Text + reader.GetString(0) + "\n"; } } CS360 Windows Programming

  13. Connecting to MySQL catch (MySqlException ex) { lb2.Text = "Exception accessing MySQL server: " + ex.Message; } catch (Exception ex) { lb2.Text = "Exception accessing database list: " + ex.Message; } finally { if (reader != null) reader.Close(); if (conn != null) conn.Close(); } CS360 Windows Programming

  14. CS360 Windows Programming

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