Mysql: Compare and filter time entries - mysql

Question

I have an table with user ids and login dates.
id | customer | timestamp
1 | 1 | 2017-02-10 11:30:28
2 | 1 | 2017-02-11 11:30:28
3 | 2 | 2017-02-12 11:30:28
4 | 3 | 2017-02-13 11:30:28
5 | 1 | 2017-02-14 11:30:28
Now I want to get the count of the longest continuous streak of logins per customer.
I got to the point, where the difference is calculated correctly for one customer.
SELECT a.id aId,
b.id bId,
a.customer,
a.timestamp aTime,
b.timestamp bTime,
DATEDIFF(b.timestamp, a.timestamp) as diff
FROM logins a
INNER JOIN logins b
ON a.customer = b.customer AND a.id < b.id
WHERE b.customer = 7
GROUP BY a.id
How can I do this for the whole table and count the following logins with a difference under 1 day?
The wanted result for this example should be:
customer | days of continuous login
1 | 2
2 | 1
3 | 1

Answer 1

You can do this with a LEFT JOIN
Query
SELECT
logins.customer
, COUNT(*) as "longest continuous streak of logins"
FROM (
SELECT
login1.*
FROM
login login1
LEFT JOIN
login login2
ON
login1.timestamp < login2.timestamp
AND
# Only JOIN if date diff is less or equal then 1 day
DATEDIFF(login2.timestamp, login1.timestamp) <= 1
WHERE
login2.id IS NOT NULL
AND
login2.customer IS NOT NULL
AND
login2.timestamp IS NOT NULL
ORDER BY
login1.customer
)
AS logins
GROUP BY
logins.customer
Result
| customer | longest continuous streak of logins |
|----------|-------------------------------------|
| 1 | 2 |
| 2 | 1 |
| 3 | 1 |
see demo http://www.sqlfiddle.com/#!9/ad581/17