如何将 SQL 查询转换为 JSON 格式

Question

I am trying to convert my SQL result into JSON format it's showing an error.

SQL Query:

 SELECT 
    User.name, 
    Course.title, 
    Member.role 
FROM User 
JOIN Member JOIN Course 
    ON User.user_id = Member.user_id 
    AND Member.course_id = Course.course_id 
ORDER BY 
    Course.title, 
    Member.role DESC, 
    User.name;

I have also tried FOR JSON PATH and FOR JSON AUTO but the following error is coming:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'for JSON AUTO' at line 1

Answer 1

You can use JSON_OBJECT() to generate valid json in MySQL.

For example, this would generate a json object for each row, with keys user_name , course_title and member_role , in a column called js :

SELECT JSON_OBJECT(
    'user_name', User.name, 
    'course_title', Course.title, 
    'member_role', Member.role 
) as js
FROM User 
JOIN Member JOIN Course 
    ON User.user_id = Member.user_id 
    AND Member.course_id = Course.course_id 
ORDER BY 
    Course.title, 
    Member.role DESC, 
    User.name;

If you want a resultset made of a single row and a single column where all objects are aggregated in an array, you can use JSON_ARRAYAGG on top of JSON_OBJECT() :

SELECT JSON_ARRAYAGG(js) js_array
FROM (
    SELECT JSON_OBJECT(
        'user_name', User.name, 
        'course_title', Course.title, 
        'member_role', Member.role 
    ) as js
    FROM User 
    JOIN Member JOIN Course 
        ON User.user_id = Member.user_id 
        AND Member.course_id = Course.course_id 
    ORDER BY 
        Course.title, 
        Member.role DESC, 
        User.name
);