PreparedStatement interface

The PreparedStatement interface is a subinterface of the java.sql.Statement interface, used to execute parameterized SQL statements. It is used to send a precompiled SQL statement to the database server, which is then used to efficiently execute the same statement multiple times with different input parameters.

With a PreparedStatement, placeholders can be used in the SQL statement that are later bound with actual values when the statement is executed. This allows for more efficient execution of multiple statements with different parameter values as the statement is compiled only once.

The PreparedStatement interface provides methods to set parameters for the placeholders, and then execute the statement with the parameter values. The result of the execution can be obtained using methods such as executeQuery(), executeUpdate(), or execute().

Using PreparedStatement interface helps to improve the performance of the application and also provides protection against SQL injection attacks, as it automatically escapes any special characters in the parameter values.

Why use PreparedStatement?

There are several reasons why you should use PreparedStatement interface instead of plain Statement interface to execute SQL statements in your Java applications. Some of them are:

Improved Performance: PreparedStatement is precompiled and cached on the database server, so when you execute the same SQL statement multiple times with different parameter values, the database server can reuse the compiled statement plan, resulting in faster execution times.
Protection Against SQL Injection: PreparedStatement provides protection against SQL injection attacks by automatically escaping any special characters in the parameter values. This helps to prevent malicious SQL code from being injected into your SQL statement.
Better Readability and Maintainability: By using PreparedStatement interface, you can separate the SQL statement from the parameter values, which makes your code more readable and maintainable.
Support for Batch Updates: PreparedStatement interface supports batch updates, which means you can execute a group of related SQL statements as a batch with a single round trip to the database server. This can significantly improve performance when you need to execute multiple SQL statements.
Support for Retrieving Generated Keys: PreparedStatement interface supports retrieving generated keys, which are automatically generated by some databases when you insert a new row into a table with an auto-increment column. You can use the getGeneratedKeys() method of PreparedStatement interface to retrieve these keys.

Overall, PreparedStatement interface is a powerful tool for executing parameterized SQL statements in your Java applications, offering improved performance, protection against SQL injection, and support for batch updates and retrieving generated keys.

How to get the instance of PreparedStatement?

To create an instance of PreparedStatement, you first need to obtain a connection to the database using a suitable implementation of the java.sql.Connection interface. Once you have a connection, you can create a PreparedStatement by calling its prepareStatement() method. The prepareStatement() method takes a SQL query as its argument and returns a new instance of PreparedStatement.

Here’s an example code snippet that shows how to create a PreparedStatement:

// Obtain a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password");

// Define a SQL query with placeholders for parameters
String sql = "SELECT * FROM mytable WHERE id = ? AND name = ?";

// Create a new instance of PreparedStatement by passing the SQL query to prepareStatement() method
PreparedStatement pstmt = conn.prepareStatement(sql);

In this example, we first obtain a connection to a MySQL database using the DriverManager.getConnection() method. We then define a SQL query with two placeholders for parameters. Finally, we create a new instance of PreparedStatement by passing the SQL query to the prepareStatement() method of the connection object.

Note that the prepareStatement() method can also take an optional second argument that specifies whether the PreparedStatement should return generated keys or not. If you need to retrieve generated keys, you can pass the constant PreparedStatement.RETURN_GENERATED_KEYS as the second argument to prepareStatement() method.

Methods of PreparedStatement interface:

The PreparedStatement interface provides several methods for setting parameter values, executing the prepared statement, and retrieving results. Some of the most commonly used methods are:

setInt(int parameterIndex, int value): Sets the value of the specified parameter as an integer.
setString(int parameterIndex, String value): Sets the value of the specified parameter as a string.
setDate(int parameterIndex, Date value): Sets the value of the specified parameter as a java.sql.Date object.
setTimestamp(int parameterIndex, Timestamp value): Sets the value of the specified parameter as a java.sql.Timestamp object.
setNull(int parameterIndex, int sqlType): Sets the value of the specified parameter to NULL.
execute(): Executes the prepared statement and returns a boolean value indicating whether the statement returned a ResultSet or not.
executeQuery(): Executes the prepared statement and returns a ResultSet object that contains the query results.
executeUpdate(): Executes the prepared statement as an update statement and returns the number of rows affected.
addBatch(): Adds the current set of parameters to the batch for execution as a single unit.
clearParameters(): Clears the values of all the parameters in the prepared statement.
getGeneratedKeys(): Retrieves any auto-generated keys created as a result of executing the prepared statement.

These are just a few examples of the methods available in the PreparedStatement interface. The full list of methods can be found in the Java API documentation.

Example of PreparedStatement interface that inserts the record:

Sure, here’s an example of using PreparedStatement interface to insert a record into a database table:

// Obtain a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password");

// Define a SQL query with placeholders for parameters
String sql = "INSERT INTO mytable (id, name, email) VALUES (?, ?, ?)";

// Create a new instance of PreparedStatement by passing the SQL query to prepareStatement() method
PreparedStatement pstmt = conn.prepareStatement(sql);

// Set the values of the parameters using the appropriate setter methods
pstmt.setInt(1, 123);   // Set the first parameter (id) as an integer value
pstmt.setString(2, "John Doe");   // Set the second parameter (name) as a string value
pstmt.setString(3, "[email protected]");   // Set the third parameter (email) as a string value

// Execute the prepared statement as an update statement and get the number of rows affected
int rowsAffected = pstmt.executeUpdate();

// Close the prepared statement and the database connection
pstmt.close();
conn.close();

In this example, we first obtain a connection to a MySQL database using the DriverManager.getConnection() method. We then define a SQL query with three placeholders for parameters to insert a record into a table named “mytable”. We create a new instance of PreparedStatement by passing the SQL query to the prepareStatement() method of the connection object.

Next, we set the values of the parameters using the appropriate setter methods of the PreparedStatement interface. We set the first parameter (id) as an integer value, the second parameter (name) as a string value, and the third parameter (email) as a string value.

Finally, we execute the prepared statement as an update statement using the executeUpdate() method of the PreparedStatement interface and get the number of rows affected. We then close the prepared statement and the database connection.

Note that this is just a simple example and in a real-world application, you would typically handle exceptions and errors, use transactions, and ensure that the connection and prepared statement are closed properly, among other things.

Example of PreparedStatement interface that updates the record:

Sure, here’s an example of using PreparedStatement interface to update a record in a database table:

// Obtain a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password");

// Define a SQL query with placeholders for parameters
String sql = "UPDATE mytable SET name = ?, email = ? WHERE id = ?";

// Create a new instance of PreparedStatement by passing the SQL query to prepareStatement() method
PreparedStatement pstmt = conn.prepareStatement(sql);

// Set the values of the parameters using the appropriate setter methods
pstmt.setString(1, "Jane Doe");   // Set the first parameter (name) as a string value
pstmt.setString(2, "[email protected]");   // Set the second parameter (email) as a string value
pstmt.setInt(3, 123);   // Set the third parameter (id) as an integer value

// Execute the prepared statement as an update statement and get the number of rows affected
int rowsAffected = pstmt.executeUpdate();

// Close the prepared statement and the database connection
pstmt.close();
conn.close();

In this example, we first obtain a connection to a MySQL database using the DriverManager.getConnection() method. We then define a SQL query with three placeholders for parameters to update a record in a table named “mytable”. We create a new instance of PreparedStatement by passing the SQL query to the prepareStatement() method of the connection object.

Next, we set the values of the parameters using the appropriate setter methods of the PreparedStatement interface. We set the first parameter (name) as a string value, the second parameter (email) as a string value, and the third parameter (id) as an integer value.

Example of PreparedStatement interface that deletes the record:

Sure, here’s an example of using PreparedStatement interface to delete a record from a database table:

// Obtain a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password");

// Define a SQL query with a placeholder for the parameter
String sql = "DELETE FROM mytable WHERE id = ?";

// Create a new instance of PreparedStatement by passing the SQL query to prepareStatement() method
PreparedStatement pstmt = conn.prepareStatement(sql);

// Set the value of the parameter using the appropriate setter method
pstmt.setInt(1, 123);   // Set the first parameter (id) as an integer value

// Execute the prepared statement as a delete statement and get the number of rows affected
int rowsAffected = pstmt.executeUpdate();

// Close the prepared statement and the database connection
pstmt.close();
conn.close();

In this example, we first obtain a connection to a MySQL database using the DriverManager.getConnection() method. We then define a SQL query with a placeholder for a parameter to delete a record from a table named “mytable”. We create a new instance of PreparedStatement by passing the SQL query to the prepareStatement() method of the connection object.

Next, we set the value of the parameter using the appropriate setter method of the PreparedStatement interface. We set the first parameter (id) as an integer value.

Finally, we execute the prepared statement as a delete statement using the executeUpdate() method of the PreparedStatement interface and get the number of rows affected. We then close the prepared statement and the database connection.

Example of PreparedStatement interface that retrieve the records of a table:

Sure, here’s an example of using PreparedStatement interface to retrieve the records of a table from a database:

// Obtain a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password");

// Define a SQL query to select all records from a table named "mytable"
String sql = "SELECT * FROM mytable";

// Create a new instance of PreparedStatement by passing the SQL query to prepareStatement() method
PreparedStatement pstmt = conn.prepareStatement(sql);

// Execute the prepared statement as a query and get the result set
ResultSet rs = pstmt.executeQuery();

// Iterate over the result set and print the values of the columns for each row
while (rs.next()) {
    int id = rs.getInt("id");
    String name = rs.getString("name");
    String email = rs.getString("email");
    System.out.println("ID: " + id + ", Name: " + name + ", Email: " + email);
}

// Close the result set, prepared statement, and database connection
rs.close();
pstmt.close();
conn.close();

In this example, we first obtain a connection to a MySQL database using the DriverManager.getConnection() method. We then define a SQL query to select all records from a table named “mytable”. We create a new instance of PreparedStatement by passing the SQL query to the prepareStatement() method of the connection object.

Next, we execute the prepared statement as a query using the executeQuery() method of the PreparedStatement interface and get the result set. We then iterate over the result set using the next() method of the ResultSet interface and print the values of the columns for each row.

Finally, we close the result set, prepared statement, and database connection.

Example of PreparedStatement to insert records until user press n:

Sure, here’s an example of using PreparedStatement to insert records into a database table until the user presses “n”:

// Obtain a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password");

// Define a SQL query with placeholders for the parameters
String sql = "INSERT INTO mytable (name, email) VALUES (?, ?)";

// Create a new instance of PreparedStatement by passing the SQL query to prepareStatement() method
PreparedStatement pstmt = conn.prepareStatement(sql);

Scanner scanner = new Scanner(System.in);

// Loop to insert records until user presses "n"
while (true) {
    System.out.print("Enter name: ");
    String name = scanner.nextLine();

    System.out.print("Enter email: ");
    String email = scanner.nextLine();

    // Set the values of the parameters using the appropriate setter methods
    pstmt.setString(1, name);
    pstmt.setString(2, email);

    // Execute the prepared statement as an insert statement and get the number of rows affected
    int rowsAffected = pstmt.executeUpdate();

    System.out.println(rowsAffected + " row(s) affected.");

    System.out.print("Do you want to insert another record? (y/n): ");
    String choice = scanner.nextLine().trim().toLowerCase();

    if (choice.equals("n")) {
        break;
    }
}

// Close the prepared statement and the database connection
pstmt.close();
conn.close();

In this example, we first obtain a connection to a MySQL database using the DriverManager.getConnection() method. We then define a SQL query with placeholders for the parameters to insert a record into a table named “mytable”. We create a new instance of PreparedStatement by passing the SQL query to the prepareStatement() method of the connection object.

Next, we use a Scanner object to read user input in a loop. Inside the loop, we set the values of the parameters using the appropriate setter methods of the PreparedStatement interface. We then execute the prepared statement as an insert statement using the executeUpdate() method of the PreparedStatement interface and get the number of rows affected.

We then ask the user if they want to insert another record, and if the user presses “n”, we break out of the loop.

Finally, we close the prepared statement and the database connection.