SQL Server : number of orders per date with day column - sql

Question

I have a query that pulls number of orders per date.
SELECT
name, CONVERT(VARCHAR(10), order_date, 120) AS order_date,
COUNT(1) AS orders
FROM
orders AS od
WHERE
id = 73
GROUP BY
CONVERT(VARCHAR(10), order_date, 120), name
ORDER BY
order_date, name
Below are the results I get when I run the query:
name order_date orders
--------------------------
20pmam 2016-07-27 39
20pmam 2016-07-28 30
20pmam 2016-07-29 32
20pmam 2016-07-31 468
20pmam 2016-08-02 75
20pmam 2016-07-05 30
I need my results to be like this, with a new column day
name order_date orders day
-------------------------------
20pmam 2016-07-27 39 1
20pmam 2016-07-28 30 2 // days between 2016-07-27 to 2016-07-28
20pmam 2016-07-29 32 3 // days between 2016-07-27 to 2016-07-29
20pmam 2016-07-31 468 5 // days between 2016-07-27 to 2016-07-31
20pmam 2016-08-02 75 7 // days between 2016-07-27 to 2016-08-02
20pmam 2016-08-05 30 10 // days between 2016-07-27 to 2016-08-05
The first/minimum order_date should be taken as day 1 ( in the above results 2016-07-27 is day 1) and should calculate others based on the first/minimum order_date.
Is this easily possible?
I don't have any idea how to get the desired result. I would appreciate any suggestions.

Answer 1

You can do this cross apply to get the minimum date before each order_date and use it in datediff.
SELECT name,CONVERT(VARCHAR(10), order_date, 120) AS order_date, Count(1) [orders],
1+coalesce(datediff(day,t.min_date,od.order_date),0) as [Day]
FROM orders AS od
cross apply (select min(od1.order_date) as min_date
from orders od1
where od.id=od1.id and od.name=od1.name and od1.order_date<od.order_date) t
WHERE id = 73
GROUP BY CONVERT(VARCHAR(10), order_date, 120),name,datediff(day,t.min_date,od.order_date)
ORDER BY order_date,name

Answer 2

Try something like:
SELECT name,
CONVERT(VARCHAR(10), order_date, 120) AS order_date,
Count(1) AS orders,
DATEDIFF(DAY, first_order_date, order_date) + 1
FROM orders AS od
JOIN (SELECT min(order_date) AS first_order_date
FROM orders) as fod ON 1 = 1
WHERE id = 73
GROUP BY CONVERT(VARCHAR(10), order_date, 120),
name,
DATEDIFF(DAY, first_order_date, order_date) + 1
ORDER BY order_date,
name
Hope this will solve your problem