0

列を持つ非常に単純化されたテーブルが与えられた場合

  Name, Action, Status,   Timepoint
1 "A"   "Open"  "OK"      "2012-09-04 10:10:00"
2 "A"   "Close" "OK"      "2012-09-04 10:05:00"
3 "A"   "Close" "ERROR"   "2012-09-04 10:02:00"
4 "B"   "Look"  "NICE"    "2012-09-04 10:05:00"
5 "B"   "Blow"  "COLD"    "2012-09-04 10:00:00"
6 "C"   "Laugh" "OK"      "2012-09-04 10:02:00"
7 "C"   "Laugh" "MUTE"    "2012-09-04 10:00:00"

NameとActionの組み合わせの各行を最も効率的に選択するにはどうすればよいですか?ただし、最新のTimepointのActionのみを選択します。上記の例では、行を返します

1, 2, 4, 5, 6

動作中の実装は、行をフェッチし、サブクエリを使用して、新しいTimepointの同じNameとActionの組み合わせを持つ行が 0 行ある場合にのみ返します。しかし、データセットが大きくなると、それは非常に非効率に思えます。こんな感じです

SELECT Name, Action, Status, Timepoint
FROM foobar
WHERE Name IN (... Names of interest ...) AND 
Status IN (... statuses of interest ...) AND
(SELECT COUNT(*) FROM foobar AS t2 WHERE t2.Name = Name AND t2.Status = Status AND t2.Timepoint > Timepoint) = 0
order by Name, Timepoint
4

4 に答える 4

1 
Select *
from 
(
      select *,
             row_number() over (partition by Name, Action order by timepoint desc) RN
      from yourtable
) v
where RN = 1
于 2012-09-04T11:11:54.460 に答える
0 
SELECT Name, Action, Status, TimePoint
FROM foobar f1
     JOIN (SELECT Name, Status, MAX(TimePoint) as TimePoint
           FROM foobar
           GROUP BY Name, Status) f2 
          ON f1.Name = f2.Name
               AND f1.Status = f2.Status
               AND f1.TimePoint = f2.TimePoint
于 2012-09-04T11:16:54.993 に答える
0 
SELECT Name, Action, Status, MIN(Timepoint)
FROM foobar
WHERE Name IN (... Names of interest ...) AND 
Status IN (... statuses of interest ...)
GROUP BY Name, Status, Action
于 2012-09-04T11:12:53.527 に答える
0

ROW_NUMBER を使用して、必要な行を分離します。ID だけで CTE を使用してから、元のテーブルに結合するのが好きです。そうすれば、フィルタリングされる行にはそれほど多くの荷物がありません。

-- setup
DECLARE @temp TABLE(id INT,name CHAR(1),Action VARCHAR(5),Status VARCHAR(5),Timepoint DATETIME)
INSERT INTO @temp (id,name,Action,Status,Timepoint)VALUES
 (1,'A','Open','OK','2012-09-04 10:10:00')
,(2,'A','Close','OK','2012-09-04 10:05:00')
,(3,'A','Close','ERROR','2012-09-04 10:02:00')
,(4,'B','Look','NICE','2012-09-04 10:05:00')
,(5,'B','Blow','COLD','2012-09-04 10:00:00')
,(6,'C','Laugh','OK','2012-09-04 10:02:00')
,(7,'C','Laugh','MUTE','2012-09-04 10:00:00')

-- solution
;WITH groups AS
(
    SELECT
          id
        , rowNum = ROW_NUMBER() OVER(
            PARTITION BY Name,Action 
            ORDER BY Timepoint DESC)
    FROM @temp
)
SELECT temp.id, name, Action, Status, Timepoint
FROM groups INNER JOIN @temp temp ON temp.id = groups.id
WHERE rowNum = 1
于 2012-09-04T11:26:01.017 に答える