MySQL 如何通过外键 ID select 多行？

Question

调查table： enter image description here

问题table： enter image description here

我的sql查询：

SELECT s.id, q.question FROM questions q JOIN surveys s ON q.surveyId = s.id;

我的结果：

[
    {
        "id": 5,
        "question": "Which industry are you working at?"
    },
    {
        "id": 5,
        "question": "What is your company's highest annual revenue?"
    },
    {
        "id": 5,
        "question": "How long has your company been operated? updated"
    }
]

但我想要这个输出：

[
    {
        "id": 5,
        "questions": [
            "Which industry are you working at?",
            "What is your company's highest annual revenue?",
            "How long has your company been operated?"
        ]
    }
]

enter image description here

Answer 1

你要的是GROUP BY

SELECT 
  s.id, 
  JSON_ARRAYAGG(q.question)
FROM 
  questions q 
JOIN 
  surveys s ON q.surveyId = s.id;
GROUP BY
  s.id

这可能会非常接近您想要的，但是您需要 MySQL 8.0.14 或更高版本。看看 JSON_ARRAYAGG()。可以使用其他聚合函数，但您需要对结果做一些处理。

不过 GROUP BY 是必不可少的。

MySQL 如何通过外键 ID select 多行？

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