Grouping by time intervals with non-fixed ranges in MySQL

Question

I'm trying to write a query that will scan through a database of connection attempts and find a group of records that exceed x attempts within 1 hour of time.

However, these one-hour ranges can't be fixed (i.e. not just 6:00-7:00, but 6:01-7:01, 6:15-7:15, etc.)

Here's an illustration

Given Max Attempts per hour = 2

num Date
1   5:58  
2   6:09  
3   6:30
4   8:00
5   9:01
6   9:40
7   9:50
8   9:55
9   11:20

In this example, the query would return the rows 1, 2, 3, 5, 6, 7, because (1, 2, 3) and (5, 6, 7, 8) were within 1 hour of eachother and total more than 2 attempts.

Answer 1

SELECT num FROM table t1
WHERE EXISTS (
    SELECT 1 FROM table t2
    WHERE t2.num <> t1.num
    AND TIMESTAMPDIFF(MINUTE,t1.date,t2.date) <= 60
)

The query below should be faster especially if your date column is indexed

SELECT num FROM table t1
WHERE (MINUTE(TIMEDIFF((SELECT MAX(t2.date) 
    FROM table t2 
    WHERE t2.num <> t1.num 
    AND t2.date < t1.date),t1.date)) <= 60)
OR (MINUTE(TIMEDIFF((SELECT MIN(t2.date) 
    FROM table t2 
    WHERE t2.num <> t1.num 
    AND t2.date > t1.date),t1.date)) <= 60)