How to insert data in table using JDBC in java Program -

import java.sql.*;

class InsertPrepared
{
    public static void main(String args[])
    {
        try
        {
            Class.forName("oracle.jdbc.driver.OracleDriver");

            Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe", "system", "oracle");

            PreparedStatement stmt = con.prepareStatement("insert into Emp values(?,?)");

            stmt.setInt(1, 101);  // 1 specifies the first parameter in the query
            stmt.setString(2, "Ratan");

            int i = stmt.executeUpdate();
            System.out.println(i + " records inserted");

            con.close();
        }
        catch (Exception e)
        {
            System.out.println(e);
        }
    }
}

Step by Step:

1. Importing Required Classes:

import java.sql.*;

The java.sql package is being imported. Classes like Connection, Statement, PreparedStatement, etc are being used in order to talk to a database.

2. Class Declaration

class InsertPrepared {

In the above class it is this class InsertPrepared that holds the whole program in it.

3. Main Method

public static void main(String args[]) {

The main method is the entry point of the program. The execution of the program starts from this method.

4. Try-Catch Block for Error Handling:

try {

A try-catch block is used to handle exceptions such as SQLExceptions. If an error occurs during database operations, it is caught in the catch block.

5. Loading the Oracle JDBC Driver:

Class.forName(“oracle.jdbc.driver.OracleDriver”);

The Class.forName() method invokes Oracle JDBC driver (oracle.jdbc.driver.OracleDriver). It is required to make a connection with Oracle JDBC.

6. Establishing the Database Connection:

Connection con = DriverManager.getConnection(“jdbc:oracle:thin:@localhost:1521:xe”, “system”, “oracle”);

DriverManager.getConnection() is used to connect to the Oracle database.
The connection string jdbc:oracle:thin:@localhost:1521:xe connects to the database at localhost, using port 1521 and the XE database (Oracle Express Edition).
The database credentials used are:

Username: system

Password: oracle

7. Creating a PreparedStatement:

PreparedStatement stmt = con.prepareStatement(“insert into Emp values(?, ?)”);

A PreparedStatement is created with the SQL query insert into Emp values(?, ?) where ? are placeholders for the values to be inserted. This allows the use of parameters and helps avoid SQL injection.
stmt is a PreparedStatement object that will be used to execute the SQL query.

8. Setting Values for Parameters:

stmt.setInt(1, 101); // 1 specifies the first parameter in the query

stmt.setString(2, “Ratan”);

stmt.setInt(1, 101) sets the first parameter (position 1) of the PreparedStatement to the integer 101.
stmt.setString(2, “Ratan”) sets the second parameter (position 2) of the PreparedStatement to the string “Ratan”.
These values will be inserted into the Emp table.

9. Executing the Update:

int i = stmt.executeUpdate();

stmt.executeUpdate() executes the SQL query (insert operation) and returns the number of rows affected by the query.
Since we are inserting a single record, i will be 1 if the insertion is successful.

10. Print Number of Records Inserted:

System.out.println(i + ” records inserted”);

It is a statement that prints the number of records inserted. As it requires one record, it will print 1 record inserted.

11. Close the Connection:

con.close();

The resources used by the connection are released after the completion of the database operation with the help of con.close().

12. Handling Exceptions:

catch (Exception e) {

System.out.println(e);

}

If any exceptions occur (e.g., SQLException), they are caught in the catch block, and the exception message is printed.

Summary of the Process:

1. The Oracle JDBC driver is loaded.

2. A connection to the Oracle database is established using the credentials provided.

3. A PreparedStatement object is created to execute the INSERT query.

4. The values 101 and “Ratan” are set for the placeholders in the query.

5. The query is executed, which inserts a record into the Emp table.

6. The number of affected rows is printed to the console, which is 1.

7. The database connection is closed.

Example Output:

Suppose the Emp table has two columns, say emp_id and emp_name. Then the output will be as follows:

1 record inserted

This shows that one record with emp_id 101 and emp_name “Ratan” has been successfully inserted into the Emp table.

Possible Errors/Issues:

1. The SQLException will arise when the Emp table does not exist or there are some problems with your connection (maybe your username/password is wrong or database has gone down).

2. Driver Not Found: In case the Oracle JDBC driver was not properly included in your classpath, it will throw a ClassNotFoundException.

Improvements:

1. Use of finally Block: The final block could be added to guarantee the successful closing of the database connection even after an exception.

2. Parameterized Query: The current program uses a parameterized query, which will be safer and more efficient when inserting data.