How can I get only one row per record in master table?

南楼画角 提交于 2019-11-28 14:32:31

Firebird 2.0 supports the CASE expression, so you can use:

  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
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;
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