我有下表
ID location date
-- -------- -----
01 loc#1 10-06-2014
05 loc#1 11-06-2014
06 loc#2 13-06-2014
08 loc#2 14-06-2014
10 loc#2 15-06-2014
14 loc#1 16-06-2014
17 loc#1 17-06-2014
20 loc#1 18-06-2014
我需要的是获取每个位置以及在ID的顺序上提到该位置的相邻记录的数量
IE
location count(location)
-------- ---------------
loc#1 2
loc#2 3
loc#1 3
使用count + group by的问题在于,它对同一位置的所有记录进行计数,而不仅仅是相邻位置,并且输出唯一的一组位置
IE
select location, count(location) from table group by location order by ID
location count(location)
-------- ---------------
loc#1 5
loc#2 3
任何想法如何获得正确的查询?因为我不想以编程方式制作它,因为我正在使用iPhone上的数千条记录,这会产生性能问题
select minAdjLoc.ID, max(minAdjLoc.location) 'Loc', count(distinct adjLocs.ID) 'Count'
from test minAdjLoc -- Minimum record in each adjacent group
inner join test adjLocs -- All adjacent record, including self
on adjLocs.location = minAdjLoc.location
and adjLocs.ID >= minAdjLoc.ID
left join test intruder -- Possible intruder with different location
on intruder.location <> minAdjLoc.location
and intruder.ID > minAdjLoc.ID
and intruder.ID < adjLocs.ID
left join test lowerThanMin -- Possible record lower than minAdjLoc
on lowerThanMin.ID < minAdjLoc.ID
and lowerThanMin.location <> minAdjLoc.location
left join test lowerIntruder
on (lowerThanMin.ID is null or lowerThanMin.ID < lowerIntruder.ID)
and lowerIntruder.ID < minAdjLoc.ID
and lowerIntruder.location = minAdjLoc.location
where intruder.ID is null -- There can't be any record with a different location inside the group
and lowerIntruder.ID is null -- Ensure minAdjLoc is in fact the record with minimum ID
group by minAdjLoc.ID --The minimum ID of the adjacent group is unique
order by minAdjLoc.ID
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我来说两句