Fetch Recent Orders with a refcursor Using a PostgreSQL function

Return Orders Cursor

Write a PostgreSQL query to create a function that opens a cursor and returns a result set of orders placed in the last month.

Solution:

-- Create or replace a function named get_recent_orders
CREATE OR REPLACE FUNCTION get_recent_orders() 
-- Specify that the function returns a refcursor
RETURNS refcursor AS $$
-- Declare the variables for the function
DECLARE
    -- Declare a refcursor variable named cur
    cur refcursor;
-- Begin the function execution block
BEGIN
    -- Open the refcursor cur for the following query
    OPEN cur FOR 
    -- Select all columns from the Orders table
    SELECT * FROM Orders 
    -- Filter orders where the order_date is within the last month
    WHERE order_date >= CURRENT_DATE - INTERVAL '1 month';
    -- Return the opened refcursor cur
    RETURN cur;
-- End the function execution block
END;
$$ LANGUAGE plpgsql;

Explanation:

• Purpose of the Query:
• The goal is to provide a cursor that points to orders from the last month.
• This demonstrates how to work with cursors for large result sets.
• Key Components:
• DECLARE cur refcursor; : Declares a cursor variable.
• OPEN cur FOR SELECT ... : Opens the cursor for the specified query.
• Real-World Application:
• Useful when dealing with large datasets that require iterative processing or streaming.

Notes:

• Ensure that the Orders table contains an order_date column.
• Cursors can improve performance for processing large volumes of data.

For more Practice: Solve these Related Problems:

• Write a PostgreSQL function to open a cursor that returns orders placed in the last week with support for pagination.
• Write a PostgreSQL function to open a cursor that returns orders with a status of 'pending' sorted by order date.
• Write a PostgreSQL function to open a cursor that returns orders and computes a priority based on order total.
• Write a PostgreSQL function to open a cursor that returns orders placed by a specific customer within the last month.

Go to:

• Practical Techniques for Returning Result Sets in PostgreSQL Exercises Home. ↩
• PostgreSQL Exercises Home ↩

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