如何在主表中每个记录只获得一行？

Question

在多表查询中，每条记录只能获得一行吗？

我有这三张桌子：

APPLES

ID | APPLE
----------
1  | RED
2  | YELLOW
3  | GREEN

农场

ID  | FARM
--------------------
B1  | GEORGE'S FARM
B2  | JOHN'S FARM

FARM_APPLES

FARM  | APPLE
---------------
B1    | 1
B1    | 2
B1    | 3
B2    | 1
B3    | 3

使用这个表我需要这个结果：

FARM_NAME | APPLE_1 | APPLE_2 | APPLE_3
----------------------------------------
B1        | 1       | 2       | 3
B2        |1        |         | 3

非常感谢任何帮助，提前谢谢。

修改

感谢OMG小马和比尔，我会尝试你的两个解决方案，最后一件事，它可以得到这个结果：

FARM          | RED | YELLOW | GREEN
-------------------------------------
GEORGE'S FARM | YES |  YES   |  YES
JOHN's FARM   | YES |  NO    |  YES

Answer 1

Firebird 2.0 supports the CASE expression，您可以使用：

  SELECT fa.farm AS farm_name,
         MAX(CASE WHEN fa.apple = 1 THEN fa.apple ELSE NULL END AS apple_1,
         MAX(CASE WHEN fa.apple = 2 THEN fa.apple ELSE NULL END AS apple_2,
         MAX(CASE WHEN fa.apple = 3 THEN fa.apple ELSE NULL END AS apple_3,
    FROM FARM_APPLES fa
GROUP BY fa.farm

Answer 2

SELECT F.ID AS FARM_NAME,
  A1.APPLE AS APPLE_1,
  A2.APPLE AS APPLE_2,
  A3.APPLE AS APPLE_3
FROM FARMS AS F
LEFT OUTER JOIN FARM_APPLES AS A1 ON F.ID = A1.FARM AND A1.APPLE = 1
LEFT OUTER JOIN FARM_APPLES AS A2 ON F.ID = A2.FARM AND A2.APPLE = 2
LEFT OUTER JOIN FARM_APPLES AS A3 ON F.ID = A3.FARM AND A3.APPLE = 3;