Date Interval SQL

Question

I have a database that contains Freight Data. I am trying to get the three ship countries with the highest average freight charges. I want to use only the last 12 months of order data, using as the end date the last Order Date in the Orders table. The first 10 entries of the Orders table are:

I am not able to figure out how to create the condition for the starting date. The query that I wrote is:

SELECT ShipCountry, ROUND(AVG(Freight),2) AS AverageFreight
FROM [dbo].[Orders]
WHERE YEAR(OrderDate) < YEAR(MAX(OrderDate)) 
GROUP BY ShipCountry
ORDER BY AverageFreight DESC

The error that I'm getting with this query is:

An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference.

UPDATE

I resolved this problem by using the following query:

SELECT TOP 3 ShipCountry, ROUND(AVG(Freight), 2) AS AverageFreight
FROM [dbo].[Orders]
WHERE OrderDate >= (SELECT DATEADD(mm,-12,(SELECT MAX(OrderDate) FROM [dbo].[Orders]))) 
GROUP BY ShipCountry
ORDER BY AverageFreight DESC

You may edit your question and include your query as your own answer. — Tim Biegeleisen, Dec 27 '20 at 02:48
I removed the inconsistent database tags. Please tag only with the database you are really using. — Gordon Linoff, Dec 27 '20 at 03:25

score 0 · Answer 1 · answered Dec 27 '20 at 12:47

You can do this with window functions:

SELECT ShipCountry, ROUND(AVG(Freight),2) AS AverageFreight
FROM (SELECT o.*, MAX(OrderDate) OVER() as MaxOrderDate FROM [dbo].[Orders] o) o
WHERE OrderDate >= DATEADD(year, -1, MaxOrderDate) 
GROUP BY ShipCountry
ORDER BY AverageFreight DESC

score 0 · Accepted Answer · answered Dec 30 '20 at 05:45

I resolved this problem by using the following query:

SELECT TOP 3 ShipCountry, ROUND(AVG(Freight), 2) AS AverageFreight
FROM [dbo].[Orders]
WHERE OrderDate >= (SELECT DATEADD(mm,-12,(SELECT MAX(OrderDate) FROM [dbo].[Orders]))) 
GROUP BY ShipCountry
ORDER BY AverageFreight DESC

Date Interval SQL

2 Answers2