[英]How do I select the first row per group in an SQL Query?
我有這個 SQL 查詢:
SELECT Foo, Bar, SUM(Values) AS Sum
FROM SomeTable
GROUP BY Foo, Bar
ORDER BY Foo DESC, Sum DESC
這導致 output 與此類似:
47 1 100
47 0 10
47 2 10
46 0 100
46 1 10
46 2 10
44 0 2
我只想每個 Foo 的第一行(它和它的最高 Bar),並忽略 rest。
47 1 100
46 0 100
44 0 2
我怎么做?
declare @sometable table ( foo int, bar int, value int )
insert into @sometable values (47, 1, 100)
insert into @sometable values (47, 0, 10)
insert into @sometable values (47, 2, 10)
insert into @sometable values (46, 0, 100)
insert into @sometable values (46, 1, 10)
insert into @sometable values (46, 2, 10)
insert into @sometable values (44, 0, 2)
;WITH cte AS
(
SELECT Foo, Bar, SUM(value) AS SumValue, ROW_NUMBER() OVER(PARTITION BY Foo ORDER BY FOO DESC, SUM(value) DESC) AS RowNumber
FROM @SomeTable
GROUP BY Foo, Bar
)
SELECT *
FROM cte
WHERE RowNumber = 1
我可能不同意rjmunru,因為使用Ansii樣式連接通常比子查詢更容易閱讀,但對於他自己的每個 - 我只是按照我們的DBA所說的去做。
如果您只想要查詢的第一個結果,您可能可以使用rownum(如果使用oracle,其他數據庫可能有類似的東西)。
select * from foo_t f其中f.bar ='bleh'和rownum = 1
當然,HAVING子句也可能是合適的,具體取決於您要做的事情。
“HAVING用於對GROUP BY創建的組執行類似於基本SQL語句中行的WHERE子句的操作.WHERE子句限制計算的行.HAVING子句限制返回的分組行。”
心連心
只需將Players.Nick單獨分組,然后選擇描述的第一個(最小)
SELECT Players.Nick, MIN(Reasons.Description), SUM(Marks.Value) AS Sum
FROM Marks INNER JOIN
Players ON Marks.PlayerID = Players.ID INNER JOIN
Reasons ON Marks.ReasonId = Reasons.ID
GROUP BY Players.Nick
ORDER BY Players.Nick, Sum DESC
那就是如果你總是想要第一個不知道它
這是一個老帖子,但今天我遇到了同樣的問題。 我通過嘗試許多查詢來解決它,直到它工作。 我正在使用SQL Compact 3.5和visual basic 2010。
此示例適用於名為“TESTMAX”的表,其中包含“Id”(主鍵),“nom”(名稱)和“value”列,您可以使用此示例獲取每個“nom”的最大“value”行:
SELECT TESTMAX.Id, TESTMAX.NOM, TESTMAX.Value
FROM TESTMAX INNER JOIN
TESTMAX AS TESTMAX_1 ON TESTMAX.NOM = TESTMAX_1.NOM
WHERE (TESTMAX.Value IN
(SELECT MAX(Value) AS Expr1
FROM TESTMAX AS TESTMAX_2
WHERE (NOM = TESTMAX_1.NOM)))
GROUP BY TESTMAX.Id, TESTMAX.NOM, TESTMAX.Value
如果要刪除其他行,還可以使用:
DELETE FROM TESTMAX
WHERE (Id NOT IN
(SELECT TESTMAX_3.Id
FROM TESTMAX AS TESTMAX_3 INNER JOIN
TESTMAX AS TESTMAX_1 ON TESTMAX_3.NOM = TESTMAX_1.NOM
WHERE (TESTMAX_3.Value IN
(SELECT MAX(Value) AS Expr1
FROM TESTMAX AS TESTMAX_2
WHERE (NOM = TESTMAX_1.NOM)))
GROUP BY TESTMAX_3.Id, TESTMAX_3.NOM, TESTMAX_3.Value))
(已編輯基於已編輯的問題)然后,由於您希望根據聚合列的值進行過濾,因此您需要的是具有條款。
SELECT p.Nick, r.Description, SUM(m.Value) Sum
FROM Marks m
JOIN Players p
ON m.PlayerID = p.ID
JOIN Reasons r
ON m.ReasonId = r.ID
GROUP BY p.Nick, r.Description
Having SUM(m.Value) =
(Select Max(Sum) From
(SELECT SUM(m.Value) Sum
FROM Marks mi
JOIN Players pi
ON mi.PlayerID = pi.ID
JOIN Reasons r i
ON mi.ReasonId = ri.ID
Where pi.Nick = p.Nick
GROUP BY pi.Nick, ri.Description))
Order By p.Nick, Sum Desc
通常,嘗試使用子查詢而不是連接和分組 - 它通常使SQL更容易理解。
SELECT Nick,
(SELECT Description from Reasons WHERE Reasons.ID = (
SELECT FIRST(Marks.ReasonId) from Marks WHERE Marks.PlayerID = Players.ID)
),
(SELECT SUM(Value) from Marks WHERE Marks.PlayerID = Players.ID)
這是使用'HAVING'條款的機會嗎? (你想區分聚合函數 - 'Sum')?
好奇。 只有這樣才能讓它工作才能在內存中使用臨時保存表。 (TSQL語法)
-- original test data
declare @sometable table ( foo int, bar int, value int )
insert into @sometable values (1, 5, 10)
insert into @sometable values (1, 4, 20)
insert into @sometable values (2, 1, 1)
insert into @sometable values (2, 1, 10)
insert into @sometable values (2, 1, 1)
insert into @sometable values (2, 2, 13)
insert into @sometable values (3, 4, 25)
insert into @sometable values (3, 5, 1)
insert into @sometable values (3, 1, 1)
insert into @sometable values (3, 1, 1)
insert into @sometable values (3, 1, 1)
insert into @sometable values (3, 1, 1)
insert into @sometable values (3, 1, 1)
-- temp table for initial aggregation
declare @t2 table (foo int, bar int, sums int)
insert into @t2
select foo, bar, sum(value)
from @sometable
group by foo, bar
-- final result
select foo, bar, sums
from @t2 a
where sums =
(select max(sums) from @t2 b
where b.foo = a.foo)
SQL Server 2005你可以使用這個:
聲明@sometable表(foo int,bar int,value int)
插入@sometable值(1,5,10)插入@sometable值(1,4,20)插入@sometable值(2,1,1)插入@sometable值(2,1,10)插入@sometable值(2,1,1)插入@sometable值(2,2,1)插入@sometable值(3,4,25)插入@sometable值(3,5,1)插入@sometable值(3,1,1)插入@sometable值(3,1,1)插入@sometable值(3,1,1)插入@sometable值(3,1,1)插入@sometable值( 3,1,1)
- 用於初始聚合的臨時表聲明@t2表(foo int,bar int,sums int)插入@ t2選擇foo,bar,來自@sometable group的sum(value)by foo,bar
select * from(SELECT foo,bar,sums,ROW_NUMBER()OVER(PAROTION BY Foo ORDER BY Sums DESC)ROWNO from @ t2)x其中x.ROWNO = 1
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