sql用最小條件的兩列分組

Question

我有一張桌子，

| ID |ID2  | price|
+----+---+----+
| A  | AA   | 7 |
| B  | AA   | 3 |
| C  | AA   | 4 |
| D  | BB   | 7 |
| I  | BB   | 2 |
| F  | BB   | 3 |
| G  | CC   | 9 |
| E  | CC   | 4 |
| K  | CC   | 1 |

+----+---+---+

我需要通過ID2獲取下一個表組，其中包含最小字段價格和對應的最小價格字段ID1

| ID1 | ID2 | min_price |
+----+---+---+----------
| B  | AA   | 3         |
| I  | BB   | 2         |
| K  | CC   | 1         |
+----+---+---+---------

Answer 1

select a.id, a.id2, a.price from #yourtable a
 join 
    (
    select  id2, min(price) AS price 
    from #yourtable
    group by id2 
    )b 
 on a.id2=b.id2 and a.price=b.price

Answer 2

SELECT *
FROM
    #table t
    INNER JOIN (
       SELECT
          ID2
          ,MIN(price) as min_price
       FROM
          #table
       GROUP BY
          ID2
    ) g
    ON t.ID2 = g.ID2
    AND t.price = g.min_price

第1步找到最低價格，第2步返回以獲取匹配的原始記錄以獲取ID。 還有其他方法可以做到這一點。

請注意，如果您的數據集包含相同ID2中具有相同價格的2條記錄，那么將始終返回多於1條記錄。

Answer 3

根據您的解釋，我們需要按id2分組，並獲得最低價格及其對應的id。 這是相同的查詢

SELECT id,
  id2,
  price
FROM NEXT
WHERE (price,id2) IN
  (SELECT MIN(price), id2 FROM NEXT GROUP BY id2
  );

Answer 4

http://sqlfiddle.com/#!9/295702/2

SELECT t1.*
FROM t1
LEFT JOIN t1 t2
ON t1.id2=t2.id2
  AND t1.price>t2.price
WHERE t2.ID IS NULL