如何对不熟悉的行进行分组？

Question

My data looks like this: http://sqlfiddle.com/#!2/1266b2/1

But I want it to look like:

+------------+------+---+
| 2015-01-01 | walk | 1 |
| 2015-01-01 | run  | 0 |
| 2015-01-01 | bike | 0 |
| 2015-01-02 | walk | 0 |
| 2015-01-02 | run  | 0 |
| 2015-01-02 | bike | 0 |
| 2015-01-03 | walk | 0 |
| 2015-01-03 | run  | 1 |
| 2015-01-03 | bike | 0 |
| 2015-01-04 | walk | 0 |
| 2015-01-04 | run  | 0 |
| 2015-01-04 | bike | 0 |
| 2015-01-05 | walk | 0 |
| 2015-01-05 | run  | 1 |
| 2015-01-05 | bike | 0 |
+------------+------+---+

Each day should have a collection of how many occurrences of each event response happened.

• The dates are collected from a calendar table and are thus purely static.
• The event names are numerous and likely to change.
• Event responses join events for name and other context rules.

Would be a big help to figure this out. At least offer tips for better title (search terms) so I can figure out how to resolve this issue.

This is for processing graphs at activezoo.com . Any advice for other approaches or methods for analyzing data is very welcome.

Answer 1

It sounds like you want every date/event combination and you want to count the # of event responses. If so, use a cross join between the calendar and the event table to get every combination and then left join to the event_responses table and count a column from that table so you only count matches.

SELECT calendar.date AS date, events.name AS event, COUNT(event_responses.date) AS count 
FROM events
CROSS JOIN calendar
LEFT JOIN event_responses ON event_responses.event_id = events.id
AND event_responses.date = calendar.date
GROUP BY calendar.date, event
ORDER BY calendar.date, event

http://sqlfiddle.com/#!2/d2560/1