Explain the principle of bulk data update operation in a database.

The bulk update operation in a database allows changing multiple records with a single command, which is much more efficient than updating each record separately.

Working principle:

• A single SQL query is formed with a condition that covers all the necessary records (for example, UPDATE table SET column = value WHERE condition).
• The database server executes the update of all matching rows in one transaction.
• This reduces overhead for query transmission and decreases lock times.

Example in SQL:

UPDATE employees SET salary = salary * 1.1 WHERE department = 'Sales';

In Java using JDBC, it might look like this:

String sql = "UPDATE employees SET salary = salary * 1.1 WHERE department = ?";
try (PreparedStatement stmt = connection.prepareStatement(sql)) {
    stmt.setString(1, "Sales");
    int updatedRows = stmt.executeUpdate();
    System.out.println("Updated records: " + updatedRows);
}

Thus, bulk update allows efficiently and quickly changing a large amount of data with minimal resource expenditure.