PL/SQL, Oracle Corporation's proprietary procedural language extension to SQL, is a robust tool for efficient database development. It can be used for various tasks ranging from data manipulation to error handling, providing a powerful platform for developers. This article aims to explore the importance of PL/SQL, elucidate the practices that can optimize its use, and showcase how PL/SQL code can be made more efficient and maintainable.

The Role of PL/SQL in Database Development
PL/SQL is a high-performance transaction processing language that offers seamless SQL integration, server-side processing, and robust error handling capabilities. Developers can create complex procedures, functions, packages, and triggers to encapsulate business logic in the database itself, leading to improved performance and maintainability.

PL/SQL's strength lies in its ability to reduce the amount of information sent over a network through the execution of procedural statements in batches, instead of one-by-one. This significantly improves the speed of data-centric operations, especially in larger systems.

Optimizing Query Performance
Optimizing the performance of queries is a key aspect of efficient database development. One of the best practices is leveraging PL/SQL's ability to batch SQL statements. Let's take a simple example where you need to update the records of customers in a database. Instead of issuing individual update commands for each record, you can write a PL/SQL block that loops through all records and performs the update operation.

DECLARE 
  CURSOR c_customers IS
    SELECT id FROM customers;
BEGIN
  FOR r_customer IN c_customers LOOP
    UPDATE customers
    SET last_updated = SYSDATE
    WHERE id = r_customer.id;
  END LOOP;
  COMMIT;
END;

Using BULK COLLECT and FORALL statements can also significantly improve the performance of such operations.

DECLARE 
  TYPE t_ids IS TABLE OF customers.id%TYPE;
  l_ids t_ids;
BEGIN
  SELECT id BULK COLLECT INTO l_ids FROM customers;

  FORALL i IN 1..l_ids.COUNT
    UPDATE customers
    SET last_updated = SYSDATE
    WHERE id = l_ids(i);

  COMMIT;
END;

Utilizing PL/SQL Packages
PL/SQL packages provide a mechanism to group related procedures, functions, and other program objects in a single, global module. Using packages can enhance code organization, shareability, and maintainability.

CREATE OR REPLACE PACKAGE customer_package AS
  PROCEDURE update_customer_last_updated(p_customer_id customers.id%TYPE);
END customer_package;

CREATE OR REPLACE PACKAGE BODY customer_package AS
  PROCEDURE update_customer_last_updated(p_customer_id customers.id%TYPE) IS
  BEGIN
    UPDATE customers
    SET last_updated = SYSDATE
    WHERE id = p_customer_id;
  END update_customer_last_updated;
END customer_package;

In this example, the update_customer_last_updated procedure is encapsulated in a package, promoting better modularity and easier code management.

Error Handling in PL/SQL
Proper error handling in PL/SQL helps to make your code robust and reliable. PL/SQL provides exception handling that can be customized to handle specific errors or a range of errors. In the following example, a user-defined exception handles the situation when no data is found.

DECLARE 
  no_data_found EXCEPTION;
BEGIN
  SELECT salary INTO v_salary FROM employees WHERE id = 123;

  EXCEPTION
    WHEN NO_DATA_FOUND THEN
      raise_application_error(-20001, 'No employee found with ID 123');
END;

Security Considerations
Security is paramount in database development. PL/SQL can bolster the security of your database in several ways. Using bind variables can prevent SQL injection, a common security vulnerability. Furthermore, Oracle provides a feature called Invoker's Rights, which means that a stored program runs with the privileges of the user who invokes it, not the user who created it. This reduces the chance of unauthorized data access.

CREATE OR REPLACE PROCEDURE show_employee_salary(p_employee_id employees.id%TYPE) AUTHID CURRENT_USER IS
  v_salary employees.salary%TYPE;
BEGIN
  SELECT salary INTO v_salary FROM employees WHERE id = p_employee_id;
  DBMS_OUTPUT.PUT_LINE('Salary: ' || v_salary);
END show_employee_salary;

In conclusion, PL/SQL is a powerful and flexible tool for database development. By optimizing query performance, effectively utilizing PL/SQL packages, implementing robust error handling, and being aware of security considerations, developers can write efficient, maintainable, and secure PL/SQL code. The power of PL/SQL lies in the hands of the developer, and with best practices in mind, it can truly be unlocked.