SQL Function with Multiple Loops

To write a function in SQL with multiple loops, you can use a combination of cursor and WHILE loop. Here's an example of how to write such a function:

-- Function to perform complex operations with multiple loops
CREATE FUNCTION complex_function()
RETURNS TABLE (output_column INT)
AS
$$
DECLARE
    cursor1 CURSOR FOR SELECT column1 FROM table1; -- Define the cursor
    cursor2 CURSOR FOR SELECT column2 FROM table2; -- Define another cursor
    variable1 INT; -- Variable for cursor1
    variable2 INT; -- Variable for cursor2
BEGIN
    OPEN cursor1; -- Open the cursor1
    OPEN cursor2; -- Open the cursor2
    
    LOOP
        FETCH NEXT FROM cursor1 INTO variable1; -- Fetch the value from cursor1
        
        IF variable1 IS NULL THEN
            EXIT; -- Exit the loop if there are no more values in cursor1
        END IF;
        
        LOOP
            FETCH NEXT FROM cursor2 INTO variable2; -- Fetch the value from cursor2
            
            IF variable2 IS NULL THEN
                EXIT; -- Exit the inner loop if there are no more values in cursor2
            END IF;
            
            -- Perform your complex operations using variable1 and variable2
            
            INSERT INTO output_table (output_column) VALUES (result); -- Store the result in an output table
            
        END LOOP; -- End of inner loop
        
        CLOSE cursor2; -- Close the cursor2
        DEALLOCATE cursor2; -- Deallocate the cursor2
        
        OPEN cursor2; -- Reopen the cursor2 to reset its position
        
    END LOOP; -- End of outer loop
    
    CLOSE cursor1; -- Close the cursor1
    DEALLOCATE cursor1; -- Deallocate the cursor1
    
    RETURN QUERY SELECT * FROM output_table; -- Return the output table
    
END;
$$
LANGUAGE plpgsql;

Example usage of the function:

SELECT * FROM complex_function();

Note: Replace column1, table1, column2, table2, and result with the actual column names and table names, and modify the complex operations according to your requirements.

Unit Testing:

• Test the function by calling it with various input values and validate if the output is as expected.
• Test the function with sample data to ensure it can handle multiple iterations and return the correct results.