11/8/05 CS360 Windows Programming 1

Databases and Data Representation

11/8/05 CS360 Windows Programming 2

Relationships

Relation: one-to-many

1 Shereen CS360-01 12

2 Doug CS300-01 11

3 Chris CS445-01 15

4 Josh CS120-01 23

5 Mike CS120-02 19

Name Course StudentsLectID

1 1 Strain 203C

2 4 Marsh 324

3 4 Strain 202

4 2 Strain 201

Building RoomLectID

Foreign key

Primary keyOfficeID

11/8/05 CS360 Windows Programming 3

Database Views

CREATE VIEW StrainOffices AS SELECT OfficeID, LectID, Room FROM Offices WHERE Building = ‘Strain’

1 1 Strain 203C

2 4 Marsh 324

3 4 Strain 202

4 2 Strain 201

Building RoomLectIDOfficeID

1 1 203C

3 4 202

4 2 201

RoomLectIDOfficeID

11/8/05 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

1 1 203C

3 4 202

4 2 201

RoomLectIDOfficeID

1 203C

RoomOfficeID

11/8/05 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’

1 1 203C

3 4 202

4 2 201

RoomNumLIdOId

11/8/05 CS360 Windows Programming 6

Database Joins

1 Shereen CS360-01 12

2 Doug CS300-01 11

3 Chris CS445-01 15

4 Josh CS120-01 23

5 Mike CS120-02 19

Name Course StudentsLectID

1 1 Strain 203C

2 4 Marsh 324

3 4 Strain 202

4 2 Strain 201

Building RoomLectID

Foreign key

Primary keyOfficeID

11/8/05 CS360 Windows Programming 7

Joins

SELECT * FROM Lectures INNER JOIN Offices ON Lecturers.LectID = Offices.LectID ORDER BY Offices.LectID

LId Name Course Students OId LId Bld Room

1 Shereen CS360-01 12 1 1 Strain 203C

2 Doug CS300-01 11 4 2 Strain 201

3 Chris CS445-01 15 3

4 Josh CS120-01 23 2 4 Marsh 324

4 Josh CS120-01 23 3 4 Strain 202

5 Mike CS120-02 19 5

11/8/05 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’

1 Shereen CS360-01 12

2 Doug CS300-01 11

3 Chris CS445-01 15

4 Josh CS120-01 23

5 Mike CS120-02 19

Name Course StudentsLectID

1 1 Strain 203C

2 4 Marsh 324

3 4 Strain 202

4 2 Strain 201

Building RoomLectIDOfficeID

1 1 John

2 1 Mike

3 1 Harry

4 2 Holly

5 2 Ron

NameLectIDAdvID

11/8/05 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.dllo I’ve placed it in CS360 Pub under MySQL

Connector\bin\.NET 1.1

11/8/05 CS360 Windows Programming 10

Connecting to MySQL

11/8/05 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;

11/8/05 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";

}

}

11/8/05 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();

}

11/8/05 CS360 Windows Programming 14