如何正确使用此查询？

Question

我的数据库中有三个表,一个用于存储用户详细信息,一个用于存储团队详细信息,另一个用于存储用户和团队ID以识别哪个团队属于用户.

我现在想从DB中获取属于所选组的所有用户.我这样做是这样的:

SELECT u.name, u.image FROM groups g, user_groups ug, users u WHERE
 g.id = ? AND ug.group_id = g.id

但我没有得到我想要的结果.正如您在上面的附图中所看到的,我在一个组中有两个用户,所以我期待在我的响应中有两个记录,但这是我得到的响应:

JSON response:

    {
  "error": false,
  "users": [
    {
      "name": "Dušan Dimitrijevi?", // This is the user from selected group, but i'm getting duplicate record
      "image": "http://192.168.42.6:8081/timster/uploads/user_images/%2018.png"
    },
    {
      "name": "Dušan Dimitrijevi?",
      "image": "http://192.168.42.6:8081/timster/uploads/user_images/%2018.png"
    },
    {
      "name": "Miroslav", // And this one too, but also duplicated
      "image": "null"
    },
    {
      "name": "Miroslav",
      "image": "null"
    },
    {
      "name": "Pera Peric",
      "image": "null"
    },
    {
      "name": "Pera Peric",
      "image": "null"
    },
    {
      "name": "Marko Markovic",
      "image": "null"
    },
    {
      "name": "Marko Markovic",
      "image": "null"
    },
    {
      "name": "Stefan Dimitrijevic",
      "image": "null"
    },
    {
      "name": "Stefan Dimitrijevic",
      "image": "null"
    },
    {
      "name": "Petar Nikolic",
      "image": "null"
    },
    {
      "name": "Petar Nikolic",
      "image": "null"
    },
    {
      "name": "Nikola Ristic",
      "image": "null"
    },
    {
      "name": "Nikola Ristic",
      "image": "null"
    }
  ]
}

所以,我想我在查询SELECT中做错了.

Answer 1

我认为您实现的关系错误,您应该根据用户ID加入user_group表.

而且,您应该考虑使用JOIN语句:

SELECT
    u.name,
    u.image
FROM
    users u
INNER JOIN
    user_groups ug
    ON ug.user_id = u.id
WHERE
    ug.group_id = ?

(我假设你的user_group表有一个user_id字段？)