使用 MySQL JSON 字段加入表

2021-11-20 00:00:00 json mysql mysql-json

我有一个存储 id 列表的 json 字段(我知道这里不是最佳实践)，我想知道是否可以在这个 JSON 字段上使用 do 操作并在 sql 中使用它们.

I have a json field that stores a list of ids (not best practice here I know), I want to know if it's possible to use do operations on this JSON field and use them in the sql.

下面是我试图实现的虚构示例，这样的事情可行吗?

Below is a fictitious example of what I'm trying to achieve, is something like this doable? 

CREATE TABLE user (
    user_id INT,
    user_name VARCHAR(50),
    user_groups JSON
);

CREATE TABLE user_group (
    user_group_id INT,
    group_name VARCHAR(50)
);

INSERT INTO user_group (user_group_id, group_name) VALUES (1, 'Group A');
INSERT INTO user_group (user_group_id, group_name) VALUES (2, 'Group B');
INSERT INTO user_group (user_group_id, group_name) VALUES (3, 'Group C');

INSERT INTO user (user_id, user_name, user_groups) VALUES (101, 'John', '[1,3]');

根据上述数据，我想设计一个查询，得到如下结果:

With the above data I would like to fashion a query that gives me the results like this:

user_id | user_name | user_group_id | group_name|
-------------------------------------------------
101     | John      | 1             | Group A
101     | John      | 3             | Group C

我正在考虑的一些伪样式 SQL 如下，但我仍然不知道这是否可行，或者 mysql 提供了哪些 JSON 函数来实现这一点

Some psuedo style SQL I'm thinking is below, though I still have no clue if this is possible, or what JSON functions mysql offers I would use to achieve this

 SELECT 
       u.user_id, 
       u.user_name, 
       g.user_group_id
       g.group_name
   FROM users u
   LEFT JOIN user_group g on g.user_group_id in some_json_function?(u.user_groups)

如果问题不清楚，请告诉我.

Let me know if the question isn't clear.

推荐答案

借助 Feras 的评论和一些摆弄:

With the help of Feras's comment and some fiddling:

  SELECT 
       u.user_id, 
       u.user_name, 
       g.user_group_id,
       g.group_name
   FROM user u
   LEFT JOIN user_group g on JSON_CONTAINS(u.user_groups, CAST(g.user_group_id as JSON), '$')

这似乎有效，请告诉我是否有更好的方法.

This appears to work, let me know if there's a better way.

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