查询返回最近连续几天的数量

Question

我有一张表来表示日历的日子。 我想要一个（好）查询（Mysql），它返回一个日历的最近连续日数，其中check = 1.

例如：

table "day"

+---------+------------+------+-------------+
|      id | date       | check| calendar_id |
+---------+-------------------+-------------+
|       1 | 2011-06-30 |    1 |           1 | 
|       2 | 2011-07-01 |    0 |           2 |
|       3 | 2011-07-02 |    1 |           1 |
|       4 | 2011-07-03 |    0 |           3 |
|       5 | 2011-07-10 |    1 |           1 |
|       6 | 2011-08-20 |    1 |           1 |
|       7 | 2011-08-25 |    1 |           5 |
|       8 | 2011-08-28 |    0 |           1 |
|       9 | 2011-08-29 |    1 |           1 |
|       10| 2011-08-30 |    1 |           1 |
|       11| 2011-08-31 |    1 |           1 |
+---------+-------------------+-------------+

对于日历nº1，查询必须返回

+--------------------+
|      number of days|
+--------------------+
|                  3 | 
+--------------------+

（2011-08-29,2011-08-30,2011-08-31）

此查询有效，但我不知道是否是一个好的

SELECT t.*, IF((@prev - INTERVAL 1 DAY = t.d or @prev is NULL) and @c <> -1, @c := @c + 1, @c := -1) AS streak, @prev := t.d
 FROM (
    SELECT date AS d
    FROM day
    WHERE calendar_id = 1
    AND check = 1
    order by d desc
 ) AS t
 INNER JOIN (
      SELECT @prev := NULL, @c := 0
 ) AS vars
 ORDER BY streak DESC limit 1