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如何在主表中每个记录只能得到一行?

pivot firebird sql

1

Eduardo Rascon · 技术社区 · 15 年前

我有三张桌子:

苹果

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

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

农场苹果

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

有了这些表,我需要这个结果:

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

如有任何帮助,我们将不胜感激。

编辑

感谢OMG Ponies和Bill,我将尝试您的两种解决方案,最后一件事,可能会得到以下结果:

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

2 回复 | 直到 15 年前

1

2

OMG Ponies 15 年前

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

  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

2

0

Bill Karwin 15 年前

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;