CBSE Class 12 Informatics Practices Database Connectivity To MySQL Worksheet

CBSE Class 12 Informatics Practices Database Connectivity To Mysql. Students can download these worksheets and practice them. This will help them to get better marks in examinations. Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

CHAPTER 8: DATABASE CONNECTIVITY TO MYSQL

MYSQL provides connectivity for client applications developed in the Java programming language

via JDBC driver, which is called “MYSQL Connector/J”.

There are four main classes in the JDBC API for database connectivity:

(i) Driver Manager Class: It locates and logs on to the database and returns a connection object.

(ii) Connection Class: It manages the communication between Java & MySQL.

(iii) Statement Class: It contains SQL string that is submitted to the database. An SQL Select

statement returns a ResultSet object that contains the data retrieved as the result of SQL

statement.

(iv) ResultSet Class: A result set is the logical set of records that are fetched from the database by

executing a query and made available to the application program. It accesses, analyzes and

converts data values returned by the SQL select statement.

Steps for Creating Database Connectivity Application:

(i) Import the package required for database programming:

import java.sql.Connection;

import java.sql.DriverManager; or import java.sql.*

import java.sql.Statement;

import java.sql.ResultSet;

(ii) Register the JDBC driver with Driver Manager:

Class.forName(“java.sql.Driver”); or Class.forName(“com.mysql.jdbc.Driver”);

(iii) Open a connection:

Connection conn = DriverManager.getConnection(“jdbc:mysql://localhost:3306/test”, “root”,

“tiger”);

Test is the name of SQL database, root is user id and tiger is MySQL password.

(iv) Execute a query: Create an object of type Statement using createStatement() method. Then

execute the SQL statement using executeQuery( ) method, in case of SELECT query, or

executeUpdate() method, in case of UPDATE, INSERT or DELETE or Create Table query. It returns an

object of resultSet type.

Statement stmt = conn.createStatement();

String sql= “Select id, name from employee”;

ResultSet rs = stmt.executeQuery(sql);

sql = “delete from employee”;

ResultSet rs = stmt.executeUpdate(sql);

ResultSet Cursor: When a ResultSet object is created, the cursor is placed just before the first row.

To move the cursor to first row use rs.next() or rs.first(). rs.next() forwards the cursor by one row –

since Initially cursor is before the first row, first rs.next() will move the cursor to first row. Any

following rs.next() commands forward the cursor by one row.

(v) Extract data from result set: This step is required if data is fetched from the database i.e., in

case of SELECT query. To retrieve the data ResultSet.get() method is used. i.e., getInt(),

getLong(), getString(), getFloat(), getDate() etc. All these method takes parameter as Column Name

or Column Index. Column Index is the order of the column.

int id = rs.getInt(“id”); // if more than one column exists in result set with same

Column Name then the first one is returned.

or int id = rs.getInt(1); // If id is first field of table.

String name = rs.getString(“name”);

Retrieving data from result set if it contains multiple rows:

Use rs.next() method. In addition to moving a result-set by one row, it also returns true if cursor is

positioned on a row and false if cursor is positioned after the last row.

int id; String name;

while (rs.next()){ id = rs.getInt(1);

name = rs.getString(2); // display or process here.}

(v) Clean up the environment: Close all database resources using close() method.

rs.close(); stmt.close(); conn.close();

Sample Questions:

1. What is a connection and a result set?

2. What does Driver Manager do?

3. Write a statement to open a connection object namely myconn for a MySQL database namely

school.

4. What are the steps to connect to a database from the Java application?

UNIT- 2: Questions & Answers

Very Short answer types questions

1. Write the expression to print the value of a variable "Sum" of type int in a label.

Ans: jLabel1.setText(“”+Sum);

2. Name any two commonly used method of ListBox.

Ans: getSelectedIndex() and getSelectedValue()

3. Write code to add an element (“IP”) to a list (MyList) at the beginning of the list.

Ans: MyList.add(0,"IP");

4. Write command to display a message dialog to display prompt as “Hi! Everybody”.

Ans: JOptionPane.showMessageDialog(null,"Hi! Everybody");

5. How would you make a combo box editable? Ans: By setting its editable property to true.

6. Name the different list type controls offered by Java Swing.

Ans: (i) jListBox (ii) jComboBox

7. In JDBC coding, what method is used to move to last record of the recordSet with name recSet?

Ans: recSet.last();

8. What is the name of event listener interface for action events?

Ans ActionPerformed

9. Name the inheritance type which is not supported by JAVA.

Ans Multiple inheritance

10. What will be the value of jTextField1 after execution of following code:

jTextField1.setText(“Computer”.subString(3,3));

Ans: put

11. Name the character set supported by Java.

Ans: Unicode.

12. What will be the value of b if initial value if a is 13 (i) b= ++a (ii) b= a++

Ans: (i) 14 (ii) 13

13. Name the 4 essential class libraries that we need to import for setting up the connection with

the database and retrieve data from the database.

Ans: DriverManager, Connection, Statement, ResultSet

14. What is Event? Ans. An Event refers to the occurrence of an activity.

15. What will be displayed in jTextArea after executing the following? jTextArea1.setText(“India \n

is a great \t country”);

Ans: India

is a great country.

16. Name any Swing control which is invisible on the Frame?

Ans: ButtonGroup

17. How one can make a text field un-editable on a frame?

Ans: jTextfield1.setEditable(false);

18. What is Message? Ans. A Message is the information/request sent to the application.

19. Which property of list box is used to add values in the list?

Ans: Model Property

Short Answers Type Questions (2 Marks)

1. What are Access Specifiers? How Access is controlled for members of Super class?

Ans: Access specifier tells a complier about the accessibility of a data member of a class in a java

program.

a) Private: Private members of a class can just be accessed inside the class and are hidden

outside the class.

b) Protected: A class member with protected access specifier can be inherited by a sub class

but is not accessed outside the parent class.

c) Public: A Class member with public access specifier is accessible outside the class.

d) Default: These members are accessible only in the class that are in the same package class

i.e., in their own classes

2. What is a Method (Function)?

Ans: A Method or function is sequence of statement which is written to perform a specific job in

the application.

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