Finding count for a Period in sql - mysql

Question

I have a table with :
user_id | order_date
---------+------------
12 | 2014-03-23
12 | 2014-01-24
14 | 2014-01-26
16 | 2014-01-23
15 | 2014-03-21
20 | 2013-10-23
13 | 2014-01-25
16 | 2014-03-23
13 | 2014-01-25
14 | 2014-03-22
A Active user is someone who has logged in last 12 months.
Need output as
Period | count of Active user
----------------------------
Oct-2013 - 1
Jan-2014 - 5
Mar-2014 - 10
The Jan 2014 value - includes Oct -2013 1 record and 4 non duplicate record for Jan 2014)

Answer 1

You can use a variable to calculate the running total of active users:
SELECT Period,
#total:=#total+cnt AS `Count of Active Users`
FROM (
SELECT CONCAT(MONTHNAME(order_date), '-', YEAR(order_date)) AS Period,
COUNT(DISTINCT user_id) AS cnt
FROM mytable
GROUP BY Period
ORDER BY YEAR(order_date), MONTH(order_date) ) t,
(SELECT #total:=0) AS var
The subquery returns the number of distinct active users per Month/Year. The outer query uses #total variable in order to calculate the running total of active users' count.
Fiddle Demo here

Answer 2

I've got two queries that do the thing. I am not sure which one's the fastest. Check them aginst your database:
SQL Fiddle
Query 1:
select per.yyyymm,
(select count(DISTINCT o.user_id) from orders o where o.order_date >=
(per.yyyymm - INTERVAL 1 YEAR) and o.order_date < per.yyyymm + INTERVAL 1 MONTH) as `count`
from
(select DISTINCT LAST_DAY(order_date) + INTERVAL 1 DAY - INTERVAL 1 MONTH as yyyymm
from orders) per
order by per.yyyymm
Results:
| yyyymm | count |
|---------------------------|-------|
| October, 01 2013 00:00:00 | 1 |
| January, 01 2014 00:00:00 | 5 |
| March, 01 2014 00:00:00 | 6 |
Query 2:
select DATE_FORMAT(order_date, '%Y-%m'),
(select count(DISTINCT o.user_id) from orders o where o.order_date >=
(LAST_DAY(o1.order_date) + INTERVAL 1 DAY - INTERVAL 13 MONTH) and
o.order_date <= LAST_DAY(o1.order_date)) as `count`
from orders o1
group by DATE_FORMAT(order_date, '%Y-%m')
Results:
| DATE_FORMAT(order_date, '%Y-%m') | count |
|----------------------------------|-------|
| 2013-10 | 1 |
| 2014-01 | 5 |
| 2014-03 | 6 |

Answer 3

The best thing I could do is this:
SELECT Date, COUNT(*) as ActiveUsers
FROM
(
SELECT DISTINCT userId, CONCAT(YEAR(order_date), "-", MONTH(order_date)) as Date
FROM `a`
ORDER BY Date
)
AS `b`
GROUP BY Date
The output is the following:
| Date | ActiveUsers |
|---------|-------------|
| 2013-10 | 1 |
| 2014-1 | 4 |
| 2014-3 | 4 |
Now, for every row you need to sum up the number of active users in previous rows.
For example, here is the code in C#.
int total = 0;
while (reader.Read())
{
total += (int)reader['ActiveUsers'];
Console.WriteLine("{0} - {1} active users", reader['Date'].ToString(), reader['ActiveUsers'].ToString());
}
By the way, for the March of 2014 the answer is 9 because one row is duplicated.

Answer 4

Try this, but thise doesn't handle the last part: The Jan 2014 value - includes Oct -2013
select TO_CHAR(order_dt,'MON-YYYY'), count(distinct User_ID ) cnt from [orders]
where User_ID in
(select User_ID from
(select a.User_ID from [orders] a,
(select a.User_ID,count (a.order_dt) from [orders] a
where a.order_dt > (select max(b.order_dt)-365 from [orders] b where a.User_ID=b.User_ID)
group by a.User_ID
having count(order_dt)>1) b
where a.User_ID=b.User_ID) a
)
group by TO_CHAR(order_dt,'MON-YYYY');

Answer 5

This is what I think you are looking for
SET #cnt = 0;
SELECT Period, #cnt := #cnt + total_active_users AS total_active_users
FROM (
SELECT DATE_FORMAT(order_date, '%b-%Y') AS Period , COUNT( id) AS total_active_users
FROM t
GROUP BY DATE_FORMAT(order_date, '%b-%Y')
ORDER BY order_date
) AS t
This is the output that I get
Period total_active_users
Oct-2013 1
Jan-2014 6
Mar-2014 10
You can also do COUNT(DISTINCT id) to get the unique Ids only
Here is a SQL Fiddle