Databases and Data
Representation
11/8/05
CS360 Windows Programming
1
Relationships
 Relation: one-to-many
LectID Name
Course
1
Shereen CS360-01
Students
12
2
Doug
CS300-01
11
3
Chris
CS445-01
15
4
Josh
CS120-01
23
5
Mike
CS120-02
19
OfficeID LectID
Primary key 1
1
Building
Strain
Room
203C
2
4
Marsh
324
3
4
Strain
202
4
2
Strain
201
Foreign key
11/8/05
CS360 Windows Programming
2
Database Views
 CREATE VIEW StrainOffices AS
SELECT OfficeID, LectID, Room
FROM Offices
WHERE Building = ‘Strain’
OfficeID LectID
1
1
Building
Strain
Room
203C
2
4
Marsh
324
3
4
Strain
202
4
2
Strain
201
11/8/05
OfficeID LectID
1
1
Room
203C
3
4
202
4
2
201
CS360 Windows Programming
3
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
OfficeID LectID Room
 SELECT OfficeID, Room
FROM StrainOffices
WHERE LectID = 1
1
1
203C
3
4
202
4
2
201
OfficeID Room
1
203C
11/8/05
CS360 Windows Programming
4
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’
11/8/05
OId
1
LId
3
4
202
4
2
201
CS360 Windows Programming
1
RoomNum
203C
5
Database Joins
LectID Name
Course
1
Shereen CS360-01
Students
12
2
Doug
CS300-01
11
3
Chris
CS445-01
15
4
Josh
CS120-01
23
5
Mike
CS120-02
19
OfficeID LectID
Primary key 1
1
Building
Strain
Room
203C
2
4
Marsh
324
3
4
Strain
202
4
2
Strain
201
Foreign key
11/8/05
CS360 Windows Programming
6
Joins
 SELECT * FROM Lectures INNER JOIN Offices
ON Lecturers.LectID = Offices.LectID ORDER
BY Offices.LectID
LId
1
Name
Course
Students OId LId Bld
Room
Shereen CS360-01 12
1
1 Strain 203C
2
3
4
4
Doug
Chris
Josh
Josh
CS300-01
CS445-01
CS120-01
CS120-01
5
Mike
CS120-02 19
11/8/05
11
15
23
23
4
2
3
CS360 Windows Programming
2
3
4
4
Strain 201
Marsh 324
Strain 202
5
7
Your Turn
 SELECT Name FROM Lecturers
INNER JOIN Offices ON Lecturers.LectID = Office.LectID
INNER JOIN Advisees ON Lecturers.LectID = Advisees.AdvID
WHERE Building = ‘Strain’ AND Name = ‘Harry’
LectID Name
Course
Students
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
11/8/05
AdvID
1
LectID Name
1
John
2
1
Mike
3
1
Harry
4
2
Holly
5
2
Ron
OfficeID LectID Building Room
1
1
Strain 203C
2
4
Marsh 324
3
4
Strain
202
4
2
Strain
201
CS360 Windows Programming
8
Connecting to MySQL
 C# can connect to MySQL
 Need to download a .NET connector
 http://dev.mysql.com/downloads/connector/n
et/1.0.html
 Need the MySql.Data.dll
o
11/8/05
I’ve placed it in CS360 Pub under MySQL
Connector\bin\.NET 1.1
CS360 Windows Programming
9
Connecting to MySQL
11/8/05
CS360 Windows Programming
10
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
11
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
12
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
13
11/8/05
CS360 Windows Programming
14