MySQL：从多个表中选择嵌套列表

Question

I'm working on a game where I have some images , where each image has some keywords and each keyword have a score.

I want to get all images, and it's keywords (with scores) by gameId

My database structure is like this:

Games

• id

Image

• id
• gameId
• imageUrl

Keywords

• keyword
• score
• imageId

I want to get a JSON response that looks like this:

{
    gameId: 1,
    images: [
        {
            imageId: 1,
            keywords: [
                {
                    keyword: "keyword1",
                    score: 1234
                }...
            ]
        }...
    ]
}

My SQL query looks like this:

SELECT g.*, (SELECT i.*, kw.* 
FROM image i LEFT OUTER JOIN keywords kw on kw.imageId=i.id 
where i.gameId = g.id) as images
FROM games g LEFT OUTER JOIN users u on u.id=g.byUser WHERE g.id = 1

But I get this error:

1241 - Operand should contain 1 column(s)

What am I doing wrong? Can't I nest an array in the response?

Answer 1

No you cannot nest an array in the select list.

Maybe you need this:

SELECT g.*, i.*, kw.* 
FROM games g LEFT OUTER JOIN users u on u.id=g.byUser 
             LEFT OUTER JOIN image i on i.gameId = g.id 
             LEFT OUTER JOIN keywords kw on kw.imageId = i.id
WHERE g.id = 1;

But there will be extra g.* values in some rows