1. Chapter 15
Using a Database

2. Database tables Relational database keep data in tables
do not include redundant information
Key identifies the data in a row
Sales database example has five tables
Customer, Salesperson, Item, Orders, and OrderItem

3. CustomerID CustomerName Address BalanceDue
1234
Fred Flynn
22 First St.
5678
Darnell Davis
33 Second St.
130.95
4321
Marla Martinez
44 Third St.
8765
Carla Kahn
55 Fourth St.
Figure The Customer table

4. SalespersonID SalespersonName Address12
Peter Patterson
66 Fifth St. 98
Donna Dubarian
77 Sixth St.
Figure The Salesperson table

5. ItemNumber Description Quantity
222222
radio 32
333333
television 14
444444
computer 9
Figure The Item table

6. OrderNumber CustomerID SalespersonID OrderDate1
1234 12
4/3/99 2
5678
3/22/99 3
8765 98
2/19/99 4
4/5/99 5
2/28/99
Figure The Orders table

7. OrderNumber ItemNumber Quantity UnitPrice1
222222 4
27.00
333333 2
210.50
444444
569.00
230.95 3 5
725.00
Figure The OrderItem table

8. Type Standard SQL Description
CHAR(N) Fixed size string of length N
VARCHAR(N) Variable size string up to length N
INTEGER bit integer
DATE Year, month, and day
DECIMAL Used for dollars and cents
Figure SQL data types

9. CREATE TABLE tablename
(fieldname1 TYPE1, fieldname2 TYPE2, ... , fieldnameN TYPEn)
INSERT INTO tablename
VALUES (field1value,field2value, ..., fieldNvalue)
DELETE FROM tablename
WHERE fieldname1 = value1 ... AND fieldnameN = valueN
UPDATE tablename SET fieldnameToSet = newValue
WHERE fieldname1ToCheck = value1ToCheck
SELECT fieldname1, ..., fieldnameN FROM table1, ..., tableM
WHERE condition1 ... AND conditionN
Figure Some patterns for SQL statements

10. Client1
Database
Server
Client 2
Figure Client-server database access

11. Client1
Application
Server
Database
Server
Client2
Figure A three-tiered system architecture

12. Database Drivers JDBC statements are database independent
A driver translates from JDBC to vendor’s database commands
Database vendors provide JDBC drivers
e.g Oracle, mySQL
Microsoft Access has an ODBC driver
Use JdbcOdbc bridge to convert from JDBC to ODBC driver
Must register ODBC data source

13. Connecting to Microsoft Access
String connect = "Provider=Microsoft.JET.OLEDB.4.0;“
source=
c:\booksharp\gittleman\ch15\Sales.mdb";
OleDbConnection con
= new OleDbConnection(connect);
con.Open();
Console.WriteLine
("Made the connection to the Sales database");
con.Close();

14. Creating a database Do not need C#, can do it in Access
OleDbCommand cmd = con.CreateCommand();
cmd.CommandText = “SQL here”;
cmd.ExecuteNonQuery();
SQL CREATE to create a new table
SQL INSERT to insert data

15. Retrieving Information
cmd.CommandText
= "SELECT CustomerName, Address "
+ "FROM Customer ORDER BY CustomerName";
reader = cmd.ExecuteReader();
while(reader.Read())
Console.WriteLine("{0}\t{1}",
reader.GetString(0), reader.GetString(1));
reader.Close();

16. Java method SQL type
GetInt INTEGER
GetString VARCHAR
GetDecimal DECIMAL
GetDate DATE
Figure C# methods for SQL types

17. Customer ordering computers
SELECT DISTINCT CustomerName
FROM Customer, Item, Orders, OrderItem
WHERE Customer.CustomerID = Orders.CustomerID
AND Orders.OrderNumber = OrderItem.OrderNumber
AND OrderItem.ItemNumber = Item.ItemNumber
AND Description = 'computer'

18. Database Info
The GetOleDbSchemaTable method returns information about the data set. This method has two parameters a Guid and an Object[]
The Guid is a globally unique 128-bit identifier that is unique across all computers and networks. We use OleDbSchemaGuid values. The two we illustrate are Tables and Columns. Using Tables will return a table that describes each table in the data set. Using Columns will return a table that describes each column.

19. DataSet Create a DataSet and process the data offline
Use an OleDbDataAdapter to fill the DataSet
Get the DataTable objects

20. Stored Procedures
Compile once, run many times with different parameters
cmd.CommandText
= "SELECT Quantity FROM Item "
+ "WHERE Description = ?";
OleDbParameter param = new OleDbParameter();
cmd.Parameters.Add(param);
param.Value = "radio";
OleDbDataReader reader = cmd.ExecuteReader();
while(reader.Read())
Console.WriteLine("{0}", reader.GetInt32(0));
reader.Close();

21. Transactions All parts must succeed for transaction to succeed
OleDbTransaction trans
= con.BeginTransaction();
cmd.Transaction = trans;
trans.Commit(); // if transaction succeeds
trans.Rollback(); // undoes changes from start
// or last Commit