Grouping data into ranges - mysql

Question

I have a query that returns the counts from a database. Sample output of the query:
23
14
94
42
23
12
The query:
SELECT COUNT(*)
FROM `submissions`
INNER JOIN `events`
ON `submissions`.event_id = `events`.id
WHERE events.user_id IN (
SELECT id
FROM `users`
WHERE users.created_at IS NOT NULL
GROUP BY `events`.id
Is there a way to easily take the output and split it into pre-defined ranges of values (0-100, 101-200, etc), indicating the number of rows that fall into a particular range?

Answer 1

Use a case expression in select clause.
SELECT `events`.id ,
case when COUNT(`events`.id) between 0 and 100 then '0 - 100'
when COUNT(`events`.id) between 100 and 200 then '100 - 200'
end as Range
FROM `submissions`
INNER JOIN `events`
ON `submissions`.event_id = `events`.id
WHERE events.user_id IN (
SELECT id
FROM `users`
WHERE users.created_at IS NOT NULL
GROUP BY `events`.id

Answer 2

Use conditional count by leveraging SUM() aggregate.
If you need your ranges in columns
SELECT SUM(CASE WHEN n BETWEEN( 0 AND 100) THEN 1 ELSE 0 END) '0-100',
SUM(CASE WHEN n BETWEEN(101 AND 200) THEN 1 ELSE 0 END) '101-200'
-- , add other ranges here
FROM (
SELECT COUNT(*) n
FROM submissions s JOIN events e
ON s.event_id = e.id JOIN users u
ON e.user_id = u.id
WHERE u.created_at IS NOT NULL
GROUP BY e.id
) q
Sample output
+-------+---------+
| 0-100 | 101-200 |
+-------+---------+
| 2 | 3 |
+-------+---------+
1 row in set (0.01 sec)
If you'd rather have it as a set you can do
SELECT CONCAT(r.min, '-', r.max) `range`,
SUM(n BETWEEN r.min AND r.max) count
FROM (
SELECT COUNT(*) n
FROM submissions s JOIN events e
ON s.event_id = e.id JOIN users u
ON e.user_id = u.id
WHERE u.created_at IS NOT NULL
GROUP BY e.id
) q CROSS JOIN (
SELECT 0 min, 100 max
UNION ALL
SELECT 101, 200
-- add other ranges here
) r
GROUP BY r.min, r.max
Sample output
+---------+-------+
| range | count |
+---------+-------+
| 0-100 | 2 |
| 101-200 | 3 |
+---------+-------+
2 rows in set (0.01 sec)