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Question

我在訪問如下表2010年

EQID Breaker Circuit Rating 
1 A  One  1000 
2 A  Two  1500 
3 A  Three 500 
4 A  Four 1000 
5 B  One  1500 
6 B  Two  2000 

我想通過創建一個斷路器查詢組，並顯示最低評級和相關電路爲評分。我知道如何做到這一點，而不顯示電路的最低等級。

我想要的查詢結果是：

EQID Breaker Circuit Rating 
1 A  Three 500 
2 B  One  1500 

Answer 1

試試這個：

SELECT a.* 
FROM table AS a 
INNER JOIN (
    SELECT Breaker, MIN(Rating) AS min_rating 
    FROM table 
    GROUP BY Breaker 
) AS b 
ON a.Breaker = b.Breaker AND 
    a.Rating = b.min_rating; 

SQLFiddle：http://www.sqlfiddle.com/#!2/ea4fb/2

Answer 2

您可以在下面嘗試：

SELECT t.EQID, t.Breaker, t.Circuit, t.Rating 
FROM test t 
INNER JOIN 
(
    SELECT a.Breaker, MIN(a.Rating) AS Rating 
    FROM test a 
    GROUP BY Breaker 
) AS tmp 
ON tmp.Breaker = t.Breaker AND tmp.Rating = t.Rating; 

的Sql小提琴DEM o：http://sqlfiddle.com/#!2/fe796/19