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# JDBC - Batch Processing

Batch Processing allows you to group related SQL statements into a batch and submit them with one call to the database.

When you send several SQL statements to the database at once, you reduce the amount of communication overhead, thereby improving performance.

- JDBC drivers are not required to support this feature. You should use the DatabaseMetaData.supportsBatchUpdates() method to determine if the target database supports batch update processing. The method returns true if your JDBC driver supports this feature.

- The addBatch() method of Statement, PreparedStatement, and CallableStatement is used to add individual statements to the batch. The executeBatch() is used to start the execution of all the statements grouped together.

- The executeBatch() returns an array of integers, and each element of the array represents the update count for the respective update statement.

- Just as you can add statements to a batch for processing, you can remove them with the clearBatch() method. This method removes all the statements you added with the addBatch() method. However, you cannot selectively choose which statement to remove.

# Batching with Statement Object:

Here is a typical sequence of steps to use Batch Processing with Statment Object:

1. Create a Statement object using either createStatement() methods.

2. Set auto-commit to false using setAutoCommit().

3. Add as many as SQL statements you like into batch using addBatch() method on created statement object.

4. Execute all the SQL statements using executeBatch() method on created statement object.

5. Finally, commit all the changes using commit() method.

## Example:

The following code snippet provides an example of a batch update using Statement object:

    // Create statement object
    Statement stmt = conn.createStatement();

    // Set auto-commit to false
    conn.setAutoCommit(false);

    // Create SQL statement
    String SQL = "INSERT INTO Employees (id, first, last, age) " +
                 "VALUES(200,'Zia', 'Ali', 30)";
    // Add above SQL statement in the batch.
    stmt.addBatch(SQL);

    // Create one more SQL statement
    String SQL = "INSERT INTO Employees (id, first, last, age) " +
                 "VALUES(201,'Raj', 'Kumar', 35)";
    // Add above SQL statement in the batch.
    stmt.addBatch(SQL);

    // Create one more SQL statement
    String SQL = "UPDATE Employees SET age = 35 " +
                 "WHERE id = 100";
    // Add above SQL statement in the batch.
    stmt.addBatch(SQL);

    // Create an int[] to hold returned values
    int[] count = stmt.executeBatch();

    //Explicitly commit statements to apply changes
    conn.commit();

For a better understanding, I would suggest to study Batching - Example Code.

# Batching with PrepareStatement Object:

Here is a typical sequence of steps to use Batch Processing with PrepareStatement Object:

1. Create SQL statements with placeholders.

2. Create PrepareStatement object using either prepareStatement() methods.

3. Set auto-commit to false using setAutoCommit().

4. Add as many as SQL statements you like into batch using addBatch() method on created statement object.

5. Execute all the SQL statements using executeBatch() method on created statement object.

6. Finally, commit all the changes using commit() method.

The following code snippet provides an example of a batch update using PrepareStatement object:

    // Create SQL statement
    String SQL = "INSERT INTO Employees (id, first, last, age) " +
                 "VALUES(?, ?, ?, ?)";

    // Create PrepareStatement object
    PreparedStatemen pstmt = conn.prepareStatement(SQL);

    //Set auto-commit to false
    conn.setAutoCommit(false);

    // Set the variables
    pstmt.setInt( 1, 400 );
    pstmt.setString( 2, "Pappu" );
    pstmt.setString( 3, "Singh" );
    pstmt.setInt( 4, 33 );
    // Add it to the batch
    pstmt.addBatch();

    // Set the variables
    pstmt.setInt( 1, 401 );
    pstmt.setString( 2, "Pawan" );
    pstmt.setString( 3, "Singh" );
    pstmt.setInt( 4, 31 );
    // Add it to the batch
    pstmt.addBatch();

    //add more batches
    .
    .
    .
    .
    //Create an int[] to hold returned values
    int[] count = stmt.executeBatch();

    //Explicitly commit statements to apply changes
    conn.commit();

For a better understanding, I would suggest to study Batching - Example Code.

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