MySQL: Create running sum for all dates in range? - mysql

Question

I have a table Service, that stores records of sales and referral types that led to the sale. I need to know the total number of sales that resulted from a given referral type over a range of dates. The relevant data in Service looks like the following:
+------+-------+------------+
| uuid | sr_id | s_saledate |
+------+-------+------------+
| | 1 | 2020-01-01 |
| | 1 | 2020-01-01 |
| | 2 | 2021-01-01 |
| | 2 | 2021-01-01 |
| | 1 | 2021-01-01 |
+------+-------+------------+
I want to count the number of sales for each referral type (sr_id) in a given date range.
If my date range is 2020-01-01 thru 2021-01-01, my output should be something like:
+------+-------+------------+----------------------+
| uuid | sr_id | date | num_sales_as_of_date
+------+-------+-----------------------------------+
| | 1 | 2020-01-01 | 2 |
| | 1 | 2020-01-02 | 2 |
| | 1 | 2020-01-03 | 2 |
........................................................ < many rows for days in range
1 2021-01-01 | 3
| | 2 | 2020-01-01 | 0 |
| | 2 | 2020-01-02 | 0 |
........................................................ < many rows for days in range
| | 2 | 2020-01-01 | 2 |
+------+-------+-----------------------------------+
There should be a row for each referral type on each date in the range.
Right now my query looks like:
SELECT s.sr_id,
s.s_saledate AS date,
Count(s.uuid)
OVER (
partition BY s.sr_id
ORDER BY s.s_saledate) AS num_sales_as_of_date
FROM Service s
How do I get the running sum for each referral type on days that had no Service with that particular referral type id?
*** EDIT FOR CLARIFICATION***
For example, in the first table I give there is no Service row in the Service table with sr_id = '1' AND s_saledate === "2020-01-02". There were two rows from prior days where sr_id = '1'. (2020-01-01). My output row for "2020-01-02" is:
sr_id date num_sales_as_of_date
1 | 2020-01-02 | 2 |

Answer 1

You need to left join your Services table from a table with all the dates in the range and a table with all the referral types, so that you get a row with every combination of date and referral type:
WITH RECURSIVE dates AS (
SELECT date('2020-01-01') AS date
UNION ALL
SELECT dates.date + INTERVAL 1 DAY
FROM dates
WHERE dates.date <= '2020-01-05'
)
SELECT ServiceReferral.sr_id,
dates.date,
Count(s.uuid)
OVER (
partition BY ServiceReferral.sr_id
ORDER BY dates.date) AS num_sales_as_of_date
FROM dates
CROSS JOIN ServiceReferral
LEFT JOIN Service s ON s.s_saledate=dates.date AND s.sr_id=ServiceReferral.sr_id
fiddle
If you do this a lot, it may be more convenient to create an actual table dates with all the dates from 0000-01-01 to 9999-12-31 and use that instead (selecting dates in the desired range in the where clause).