2. • Last day we learnt how to issue MySQL
queries from MySQL console.
• Today we will learn how to issue MySQL
queries from a java program.
3. JDBC
• The interface for accessing databases from
Java is JDBC. Via JDBC you maintain the
databases connection, issue database queries
and updates and receive the results.
• JDBC is an interface independently of any
database. For each database you require the
database specific implementation of the JDBC
driver.
4. MySQL JDBC driver
• To connect to MySQL from Java you have to
use the JDBC driver from MySQL. The MySQL
JDBC driver is called "MySQL Connector/J".
You should be able to find the latest MySQL
JDBC driver on this page
http://dev.mysql.com/downloads/connector/j
• The folder I gave you in the class contains that
JDBC driver.
5. • I will show you how to add this JDBC driver
into a java project using Netbeans.
• Create a new project.
• I have created a new project named
MySQLConnector.
• Go to the project properties by right click on
the project in the project window and select
the menu item ‘Properties’.
6. • A window will appear :
• Click on the Libraries option
7.
8. • There is a jar file in the folder I gave you.
Select the jar file.
• Now we are ready to write a java program that
can issue MySQL queries.
9. • Add the following code in your project.
• Here connect object sets up the connection with
database.
10. • DriverManager.getConnection("jdbc:mysql://l
ocalhost/test?","","");
• In this line test is the database name I created.
• In your case it can be different.
• The two empty strings are username and
password in MySQL.
• Their default values are empty string.
11. • Add two new lines:
• Statement class allows us to issue mysql
query.
12. • You can create a table by the following 2 lines:
• stmt.executeUpdate() can be use to issue any
create,insert,delete or update query.
• This will insert two rows in the table.
13. • To select from table
• result is the variable in which we store the
value returned by the select query.
14. • It is a ResultSet type of object.
• We can iterate through result by result.next()
method.
• And we can get the value of a column in the
current row by
result.getString(“ColumnName”).
• In this case ColumnName = username and
password.
• If the value of the column is integer then we
use result.getInt(“ColumnName”);
15. • PreparedStatement is like Statement class
which allows us issue MySQL queries.
• PreparedStatements can use variables and are
more efficient.
16. • To use PreparedStatement you need to include
following code
This will add a new row (“0705003”,”abcde”)
into the user_password table.
17. • Databases are stored in disks.
• We know that disk access time is significantly
higher than memory access time.
• Every query needs to access the database in
the disk.
• So it will be better if we issue many queries at
the same time by accessing the database
once.
18. • For this purpose we issue batches of query to
the database.
• You can create a query and add it to the batch.
• Here I added 5 queries to the batch by
addBatch() method.
• At last executeBatch() issued the 5 queries.
19. • Its good practice to close the Statement,
PreparedStatement, Connection and ResultSet
in the end of the program.
