Extracting entries from a specific month in SQL

Question

I'm trying to calculate total revenues from each customer purchase in March from a table called orders , where order_date is in format of datetime (eg 2019-03-04). However, I'm unsuccessful to obtain the results with either of the following options:

WITH cte_orders AS
(
    SELECT
        cust_id,
        SUM(order_quantity * order_cost) AS revenue
    FROM
        orders
    WHERE 
        DATEPART('month', order_date) = 3
    GROUP BY 
        cust_id
)
SELECT cust_id, revenue 
FROM cte_orders;

also

WHERE EXTRACT(month from order_date) = '03'

or

WHERE MONTH(order_date) = 03

doesn't work either. What's wrong with my syntax here?

Answer 1

Thanks everyone for the input, finally figured out the right way to do this:

WITH cte_orders AS
(
    SELECT 
        cust_id,
        SUM(order_quantity * order_cost) AS revenue,
    FROM 
        orders
    WHERE
        EXTRACT('MONTH' FROM order_date :: TIMESTAMP) = 3
    GROUP BY
        cust_id
)

SELECT cust_id, revenue 
FROM cte_orders;

with this it converted the date to timestamp and extracted March as required.

Answer 2

What about date_part ?

WITH cte_orders AS
(select cust_id
    , SUM(order_quantity * order_cost) as revenue
from orders
WHERE date_part('month',TIMESTAMP order_date) = 3
group by cust_id)

select cust_id, revenue from cte_orders;

Answer 3

Did you consider putting the WHERE clause outside of the CTE?

WITH cte_orders AS
(
    SELECT
        cust_id,
        SUM(order_quantity * order_cost) AS revenue
    FROM
        orders
    WHERE 
        DATEPART('month', order_date) = 3
    GROUP BY 
        cust_id
)
SELECT cust_id, revenue 
FROM cte_orders
WHERE MONTH(order_date) = 03;

Also, it would be helpful if you let us know what (if any) results you are getting. Are you getting an error message or is it just not returning the expected values/row count?