Question

From a database, I’m trying to find profiles that have been updated in the last X days and group them based on date.

My SQL structure looks like this:
id (int)
date_modified (date)

which produces a result something like this:

+----+---------------+  
| id | date_modified |  
+----+---------------+  
| 86 | 2012-06-22    |  
| 87 | 2012-06-22    |  
| 88 | 2012-06-22    |  
| 89 | 2012-06-22    |  
| 63 | 2011-10-31    |
| 72 | 2012-02-06    |
| 60 | 2011-10-17    |
| 71 | 2012-02-29    |
| 69 | 2011-11-18    |
| 76 | 2012-02-29    |
| 70 | 2011-11-18    |
| 75 | 2012-02-29    |
| 73 | 2012-02-06    |
| 74 | 2012-02-28    |
| 77 | 2012-02-29    |
| 80 | 2012-05-07    |
| 82 | 2012-06-12    |
| 83 | 2012-08-15    |
| 84 | 2012-09-07    |
| 85 | 2012-08-15    |
+----+---------------+

Ideally, I would want to work the query so it produces a result like this:

+-------+----------+  
| total | days_ago |  
+-------+----------+  
| 4     | 1        |
| 6     | 2        |
| 8     | 3        |  
| 12    | 7        |
| 3     | 30       |
| 55    | 90       |  
| 28    | 180      |  
| 37    | 270      |  
| 42    | 360      |  
+----+-------------+

Where it’s converting the date_modified to a number of days ago and grouping it in the increments shown above.

I’m assuming this would be possible using cases in the select query, but I’m a bit at a loss for how to go about doing it.

Answer 1

You need to use the DATEDIFF MySQL function:

DATEDIFF() returns expr1 – expr2 expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation.

In your case, it’s simply solved by using

SELECT COUNT(date_modified) as total, DATEDIFF(date_modified, NOW()) as days_ago FROM mytable GROUP BY date_modified;