Examples of Normal Select Procedure in PostgreSQL

Example 1: Procedure to Select All Columns from the “employees” Table

CREATE OR REPLACE PROCEDURE select_all_employees()
LANGUAGE plpgsql
AS $$
BEGIN
    EXECUTE 'SELECT * FROM employees;';
END;
$$;

Example 2: Procedure to Select Specific Columns with a Condition

CREATE OR REPLACE PROCEDURE select_employees_by_department(dept_id INT)
LANGUAGE plpgsql
AS $$
BEGIN
    EXECUTE 'SELECT employee_id, first_name, last_name FROM employees WHERE department_id = $1;' USING dept_id;
END;
$$;

Example 3: Procedure to Use Aggregate Functions

CREATE OR REPLACE PROCEDURE count_employees_per_department()
LANGUAGE plpgsql
AS $$
BEGIN
    EXECUTE 'SELECT department_id, COUNT(*) FROM employees GROUP BY department_id;';
END;
$$;

To execute these procedures, you can call them like regular functions:

-- Call the procedure to select all employees
CALL select_all_employees();

-- Call the procedure to select employees by department
CALL select_employees_by_department(10);

-- Call the procedure to count employees per department
CALL count_employees_per_department();

These procedures encapsulate the corresponding queries and provide a convenient way to retrieve information from the database. By calling them with the appropriate parameters, you can efficiently select all employees, filter employees by department, and count employees per department.

PostgreSQL is an open-source relational database management system with a variety of features that allow users to operate database operations and improve the speed of queries.

One of these options is the ability to write stored procedures, the SQL code that logically embeds logic for a more organized and maintained program. Here we should discuss the fundamental form of the SELECT procedure in PostgreSQL and how to state queries correctly.