MySQL 'multiple rows' 来自两个连接挑战

Question

我有以下 MySQL 查询连接另外两个表..

SELECT  plants.plant_id,
        plants.scientific_name,
        plants_features.features,
        plants_features.features_id

FROM    plants_features,
        plants2features,
        plants

WHERE   plants_features.features_id = plants2features.features_id

AND     plants2features.plant_id = plants.plant_id

我对输出很满意。

plant_id,scientific_name,features,features_id
3,"Actaea matsumurae 'White Pearl' (Bugbane)","colourful fruit",6
11,"Heuchera 'Beauty Colour' (Coral bells)","salt resistant/coastal",15
18,"Phyllostachys nigra (Black bamboo)","colourful bark",5
26,"Carex morrowii 'Silver Sceptre' (Japanese sedge)","drought tolerant",18
27,"Heuchera 'Obsidian' (Coral bells)","salt resistant/coastal",15
29,"Dianella tasmanica 'Tas Red' (Flax lily)","drought tolerant",18
38,"Stipa tenuissima (Mexican feather grass)","attractive seed-heads",2
38,"Stipa tenuissima (Mexican feather grass)","invasive/self seed/suckering",13

您可以从 plant_id '38'（底部两行）中看到它每条记录输出多行。

我的问题是伙计们，你能告诉我新的 MySQL 查询到底需要什么才能确保 'plant_id' 在一条记录中包含多行吗？

提前致谢，理查德.

Answer 1

您需要分组和 aggregation functions。您可以使用 GROUP_CONCAT 来获取逗号分隔列表：

SELECT  plants.plant_id,
        plants.scientific_name,
        GROUP_CONCAT(plants_features.features) AS features,
        GROUP_CONCAT(plants_features.features_id) AS feature_ids
FROM plants_features
JOIN plants2features
  ON plants_features.features_id = plants2features.features_id
JOIN plants
  ON plants2features.plant_id = plants.plant_id
GROUP BY plants.plant_id, plants.scientific_name;

也使用 JOIN 语法代替逗号和位置。

MySQL 'multiple rows' 来自两个连接挑战

MySQL 'multiple rows' from two joins challenge

mysql

group-concat

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