如何從mysql中僅獲取連續記錄？

Question

我有一個像下面

___________ 
id | speed 
----------- 
1 | 3 
2 | 2 
3 | 0 
4 | 0 
5 | 0 
6 | 2 
7 | 0 
8 | 0 
9 | 2 
10 | 0 

現在我想要得到的記錄，其中速度爲0，但只有3至5中是連續的，比其他任何連續記錄更大的數據庫表。我不想要7,8條記錄或第10條記錄。我怎樣才能做到這一點？

Answer 1

可能最快的方法是在掃描行時，每次速度變化時使用MySQL會話變量來增加「組」。

select n.*, @groupid:=IF(@prev_speed=speed,@groupid,@groupid+1) as groupid, @prev_speed:=speed 
from (select @groupid:=0, @prev_speed=-1) _init 
cross join n 
order by id; 

+----+-------+---------+--------------------+ 
| id | speed | groupid | @prev_speed:=speed | 
+----+-------+---------+--------------------+ 
| 1 |  3 | 1  |     3 | 
| 2 |  2 | 2  |     2 | 
| 3 |  0 | 3  |     0 | 
| 4 |  0 | 3  |     0 | 
| 5 |  0 | 3  |     0 | 
| 6 |  2 | 4  |     2 | 
| 7 |  0 | 5  |     0 | 
| 8 |  0 | 5  |     0 | 
| 9 |  2 | 6  |     2 | 
| 10 |  0 | 7  |     0 | 
+----+-------+---------+--------------------+ 

然後使用上述查詢作爲派生表，計算每個組的最低和最高ID以及行數。按行數排序組。

select min(id) as minid, max(id) as maxid, count(*) as count 
from (
    select n.*, @groupid:=IF(@prev_speed=speed,@groupid,@groupid+1) as groupid, @prev_speed:=speed 
    from (select @groupid:=0, @prev_speed=-1) _init 
    cross join n 
    order by id 
) as t1 
group by t1.groupid 
order by count desc; 

+-------+-------+-------+ 
| minid | maxid | count | 
+-------+-------+-------+ 
|  3 |  5 |  3 | 
|  7 |  8 |  2 | 
|  1 |  1 |  1 | 
|  2 |  2 |  1 | 
|  6 |  6 |  1 | 
|  9 |  9 |  1 | 
| 10 | 10 |  1 | 
+-------+-------+-------+ 

然後，使用從上述的第一行作爲另一派生表，加入到原始表中從最小值到最大值的ID範圍中的行。

select n.* 
from (
     select min(id) as minid, max(id) as maxid, count(*) as count 
     from (
       select n.*, @groupid:=IF(@prev_speed=speed,@groupid,@groupid+1) as groupid, @prev_speed:=speed 
       from (select @groupid:=0, @prev_speed=-1) _init 
       cross join n 
       order by id 
     ) as t1 
     group by t1.groupid 
     order by count desc limit 1 
) as t2 
inner join n on n.id between t2.minid and t2.maxid 

+----+-------+ 
| id | speed | 
+----+-------+ 
| 3 |  0 | 
| 4 |  0 | 
| 5 |  0 | 
+----+-------+