Cumulative count over time - mysql

Question

I have a table orders like this:
customer_id order_date
10 2012-01-01
11 2012-01-02
10 2012-01-02
12 2012-01-03
11 2012-01-04
12 2012-02-01
11 2012-02-04
13 2012-02-05
14 2012-02-06
How can I get a cumulative average over time (per month) like this:
order date count orders count customers (customer_id)
2012-01 1 1 (12)
2012-01 2 2 (10,11)
2012-02 1 2 (13,14)
2012-02 2 2 (10,12
2012-02 3 2 (11)
showing how the number of customers vs. number of orders per customer develops over time.
The following query gives me the wanted information - but not over time. How can I iterate the query over time?
SELECT number_of_orders, count(*) as amount FROM (
SELECT o.customer_id, count(*) as number_of_orders
FROM orders o
GROUP BY o.customer_id) as t1
GROUP BY number_of_orders
Update:
have now build the following PHP code to generate what I need, wonder if that could be done using cumulative counts like on http://www.freeopenbook.com/mysqlcookbook/mysqlckbk-chp-12-sect-14.html
$year = 2011;
for ($cnt_months = 1; $cnt_months <= 12; $cnt_months++) {
$cnt_months_str = ($cnt_months < 10) ? '0'.$cnt_months : $cnt_months;
$raw_query = "SELECT number_of_orders, count(*) as amount
FROM (
SELECT
o.customer_id,
count(*) as number_of_orders
FROM orders o
where Date_Format( o.order_date, '%Y%m' ) >= " . $year . "01 and Date_Format( o.order_date, '%Y%m' ) <= " . $year . $cnt_months_str . "
GROUP BY o.customer_id) as t1
GROUP BY number_of_orders";
$query = db_query($raw_query);
while ($row = db_fetch_array($query)) {
$data[$cnt_months_str][$row['number_of_orders']] = array($row['number_of_orders'], (int)$row['amount']);
}
}

Answer 1

A good starting point is
SELECT
order_date,
COUNT(*) AS distinctOrders,
COUNT(DISTINCT customer_id) AS distinctCustomers,
GROUP_CONCAT(DISTINCT customer_id ASC) AS customerIDs
FROM orders
GROUP BY order_date ASC
This will give you the order_date, the number of orders on that date, the number of customers on that date, and the list of customer ids on that date.
Just looking at a way to tally up on a month by month basis. So taking this forward I've used a subquery to tally up as it goes
SELECT
ordersPerDate.*,
IF(
MONTH(ordersPerDate.order_date)=#thisMonth,
#runningTotal := #runningTotal+ordersPerDate.distinctOrders,
#runningTotal := 0
) AS ordersInThisMonth,
#thisMonth := MONTH(ordersPerDate.order_date)
FROM
(
SELECT
#thisMonth := 0,
#runningTotal := 0
) AS variableInit,
(
SELECT
order_date,
COUNT(*) AS distinctOrders,
COUNT(DISTINCT customer_id) AS distinctCustomers,
GROUP_CONCAT(DISTINCT customer_id ASC) AS customerIDs
FROM orders
GROUP BY order_date ASC
) AS ordersPerDate
And finally to clean it up, wrapped it in yet another subquery just to return the rows desired rather than the internal variables
Grouping on individual days
SELECT
collatedData.order_date,
collatedData.ordersInThisMonth AS count_orders,
collatedData.distinctCustomers AS count_customers,
collatedData.customerIDs AS customer_ids
FROM (
SELECT
ordersPerDate.*,
IF(
MONTH(ordersPerDate.order_date)=#thisMonth,
#runningTotal := #runningTotal+ordersPerDate.distinctOrders,
#runningTotal := 0
) AS ordersInThisMonth,
#thisMonth := MONTH(ordersPerDate.order_date)
FROM
(
SELECT
#thisMonth := 0,
#runningTotal := 0
) AS variableInit,
(
SELECT
order_date,
COUNT(*) AS distinctOrders,
COUNT(DISTINCT customer_id) AS distinctCustomers,
GROUP_CONCAT(DISTINCT customer_id) AS customerIDs
FROM orders
GROUP BY order_date ASC
) AS ordersPerDate
) AS collatedData
And now finally, following additional information from the OP, the end product
Grouping on calendar months
// Top level will sanitise the output
SELECT
collatedData.orderYear,
collatedData.orderMonth,
collatedData.distinctOrders,
collatedData.ordersInThisMonth AS count_orders,
collatedData.distinctCustomers AS count_customers,
collatedData.customerIDs AS customer_ids
FROM (
// This level up will iterate through calculating running totals
SELECT
ordersPerDate.*,
IF(
(ordersPerDate.orderYear,ordersPerDate.orderMonth) = (#thisYear,#thisMonth),
#runningTotal := #runningTotal+ordersPerDate.distinctOrders*ordersPerDate.distinctCustomers,
#runningTotal := 0
) AS ordersInThisMonth,
#thisMonth := ordersPerDate.orderMonth,
#thisYear := ordersPerDate.orderYear
FROM
(
SELECT
#thisMonth := 0,
#thisYear := 0,
#runningTotal := 0
) AS variableInit,
(
// Next level up will collate this to get per year, month, and per number of orders
SELECT
ordersPerDatePerUser.orderYear,
ordersPerDatePerUser.orderMonth,
ordersPerDatePerUser.distinctOrders,
COUNT(DISTINCT ordersPerDatePerUser.customer_id) AS distinctCustomers,
GROUP_CONCAT(ordersPerDatePerUser.customer_id) AS customerIDs
FROM (
// Inner query will get the number of orders for each year, month, and customer
SELECT
YEAR(order_date) AS orderYear,
MONTH(order_date) AS orderMonth,
customer_id,
COUNT(*) AS distinctOrders
FROM orders
GROUP BY orderYear ASC, orderMonth ASC, customer_id ASC
) AS ordersPerDatePerUser
GROUP BY
ordersPerDatePerUser.orderYear ASC,
ordersPerDatePerUser.orderMonth ASC,
ordersPerDatePerUser.distinctOrders DESC
) AS ordersPerDate
) AS collatedData

Answer 2

SELECT
substr(order_date,1,7) AS order_period,
count(*) AS number_of_orders,
count(DISTINCT orders.customer_id) AS number_of_customers,
GROUP_CONCAT(DISTINCT orders.customer_id) AS customers
FROM orders
GROUP BY substr(order_date,1,7)