Generating order statistics grouped by order total - sql

Question

Hopefully I can explain this correctly. I have a table of line orders (each line order consists of quantity of item and the price, there are other fields but I left those out.)
table 'orderitems':
orderid | quantity | price
1 | 1 | 1.5000
1 | 2 | 3.22
2 | 1 | 9.99
3 | 4 | 0.44
3 | 2 | 15.99
So to get order total I would run
SELECT SUM(Quantity * price) AS total
FROM OrderItems
GROUP BY OrderID
However, I would like to get a count of all total orders under $1 (just provide a count).
My end result I would like would be able to define ranges:
under $1, $1 - $3, 3-5, 5-10, 10-15, 15.. etc;
and my data to look like so (hopefully):
tunder1 | t1to3 | t3to5 | t5to10 | etc
10 | 500 | 123 | 5633 |
So that I can present a piechart breakdown of customer orders on our eCommerce site.
Now I can run individual SQL queries to get this, but I would like to know what the most efficient 'single sql query' would be. I am using MS SQL Server.
Currently I can run a single query like so to get under $1 total:
SELECT COUNT(total) AS tunder1
FROM (SELECT SUM(Quantity * price) AS total
FROM OrderItems
GROUP BY OrderID) AS a
WHERE (total < 1)
How can I optimize this? Thanks in advance!

Answer 1

select
count(case when total < 1 then 1 end) tunder1,
count(case when total >= 1 and total < 3 then 1 end) t1to3,
count(case when total >= 3 and total < 5 then 1 end) t3to5,
...
from
(
select sum(quantity * price) as total
from orderitems group by orderid
);

Answer 2

you need to use HAVING for filtering grouped values.

Answer 3

try this:
DECLARE #YourTable table (OrderID int, Quantity int, Price decimal)
INSERT INTO #YourTable VALUES (1,1,1.5000)
INSERT INTO #YourTable VALUES (1,2,3.22)
INSERT INTO #YourTable VALUES (2,1,9.99)
INSERT INTO #YourTable VALUES (3,4,0.44)
INSERT INTO #YourTable VALUES (3,2,15.99)
SELECT
SUM(CASE WHEN TotalCost<1 THEN 1 ELSE 0 END) AS tunder1
,SUM(CASE WHEN TotalCost>=1 AND TotalCost<3 THEN 1 ELSE 0 END) AS t1to3
,SUM(CASE WHEN TotalCost>=3 AND TotalCost<5 THEN 1 ELSE 0 END) AS t3to5
,SUM(CASE WHEN TotalCost>=5 THEN 1 ELSE 0 END) AS t5andup
FROM (SELECT
SUM(quantity * price) AS TotalCost
FROM #YourTable
GROUP BY OrderID
) dt
OUTPUT:
tunder1 t1to3 t3to5 t5andup
----------- ----------- ----------- -----------
0 0 0 3
(1 row(s) affected)

Answer 4

WITH orders (orderid, quantity, price) AS
(
SELECT 1, 1, 1.5
UNION ALL
SELECT 1, 2, 3.22
UNION ALL
SELECT 2, 1, 9.99
UNION ALL
SELECT 3, 4, 0.44
UNION ALL
SELECT 4, 2, 15.99
),
ranges (bound) AS
(
SELECT 1
UNION ALL
SELECT 3
UNION ALL
SELECT 5
UNION ALL
SELECT 10
UNION ALL
SELECT 15
),
rr AS
(
SELECT bound, ROW_NUMBER() OVER (ORDER BY bound) AS rn
FROM ranges
),
r AS
(
SELECT COALESCE(rf.rn, 0) AS rn, COALESCE(rf.bound, 0) AS f,
rt.bound AS t
FROM rr rf
FULL JOIN
rr rt
ON rt.rn = rf.rn + 1
)
SELECT rn, f, t, COUNT(*) AS cnt
FROM r
JOIN (
SELECT SUM(quantity * price) AS total
FROM orders
GROUP BY
orderid
) o
ON total >= f
AND total < COALESCE(t, 10000000)
GROUP BY
rn, t, f
Output:
rn f t cnt
1 1 3 1
3 5 10 2
5 15 NULL 1
, that is 1 order from $1 to $3, 2 orders from $5 to $10, 1 order more than $15.