Get accumulated data by dates in MySQL - mysql

Question

I need to get accumulated number of users by a range of dates i.e. for a month by date. The following query works fine but I have to run it for each date and I cannot use group by date. Please advise.
MySQL version 8
Sample Data
+------------------------+
| id | Registration_Date |
+------------------------+
| 1 | 2020-05-01 |
| 2 | 2020-05-01 |
| 3 | 2020-05-02 |
| 4 | 2020-05-03 |
| 5 | 2020-05-04 |
+------------------------+
Current Query
SELECT COUNT(id) AS 'Registrations'
FROM users
WHERE DATE(Registration_Date) <= "2020-05-04";
Desired Result
+-----------------------------------+
| Registration_Date | Registrations |
+-----------------------------------+
| 2020-05-01 | 2 |
| 2020-05-02 | 3 |
| 2020-05-03 | 4 |
| 2020-05-04 | 5 |
+-----------------------------------+

Answer 1

You can use window functions to achieve the result you want, COUNTing id values on or before the current registration date. Note we use DISTINCT to avoid duplication of entries where multiple users register on the same day:
SELECT DISTINCT Registration_Date,
COUNT(id) OVER (ORDER BY Registration_Date) AS Registrations
FROM users
Output:
Registration_Date Registrations
2020-05-01 2
2020-05-02 3
2020-05-03 4
2020-05-04 5
Demo on dbfiddle
To deal with the case where there are registrations before the first reporting date of interest, you need to count registrations up to and including the first date and then for each date in the reporting period in a derived table, and then sum those in an outer query:
SELECT Reporting_Date,
SUM(Registrations) OVER (ORDER BY Reporting_Date) AS Registrations
FROM (
SELECT '2020-05-01' AS Reporting_Date, COUNT(id) AS Registrations
FROM users
WHERE Registration_Date <= '2020-05-01'
UNION
SELECT Registration_Date, COUNT(id)
FROM users
WHERE Registration_Date BETWEEN '2020-05-02' AND '2020-05-04'
GROUP BY Registration_Date
) r
Generating the result this way in general will be more efficient than wrapping the original query as a derived table as it will require fewer aggregations.
Demo on dbfiddle

Answer 2

I used Nick's answer as source and now modified it a bit to get grand total plus daily increment value.
SELECT Reporting_Date, Registrations FROM
(SELECT DISTINCT DATE(Registration_Date) AS Reporting_Date,
COUNT(id) OVER (ORDER BY DATE(Registration_Date)) AS Registrations
FROM users) AS RAW_Result
WHERE Reporting_Date BETWEEN "2020-05-01" AND "2020-05-04";
Result:
+-----------------------------------+
| Registration_Date | Registrations |
+-----------------------------------+
| 2020-05-01 | 1200 | (grand total until this date)
| 2020-05-02 | 1201 | (grand total + daily increment)
| 2020-05-03 | 1202 |
| 2020-05-04 | 1203 |
+-----------------------------------+