MYSQL- select 并将多个表合并为一个 JSON

Question

你能告诉我如何解决这个问题吗？我有 3 个数据库表。

网络。
产品。
评论。

在我添加 "comments" table 之前查询看起来像这样（按预期工作）：

SELECT networks.*, products.product, products.type 
FROM products 
JOIN networks ON products.id=networks.product_Id

现在我尝试用额外的 table 修改它，但它不起作用：

SELECT 
    networks.*, 
    products.product, 
    products.type, 
    comments.id AS comment_Id, 
    comments.newLine, 
    comments.lineComment AS comment, 
    comments.topComment, 
    comments.bottomComment 
JOIN networks ON products.id=networks.product_Id, 
ON comments.id=networks.comment_Id

我该如何修正这个查询？

感谢各位帮手:)

Answer 1

我认为这就是您所追求的语法：

SELECT 
    n.*, 
    p.product, 
    p.type,
    c.id AS comment_id, 
    c.newLine, 
    c.lineComment AS comment, 
    c.topComment, 
    c.bottomComment 
FROM products p
INNER JOIN networks n ON p.id = n.product_id
INNER JOIN comments c ON c.id = n.comment_id

即：多重连接的语法是FROM ... JOIN ... ON ... JOIN ... ON ...。

请注意，使用 table 别名可缩短查询并使其更易于读写。

Answer 2

您加入了网络 table，条件是 products.id=networks.product_Id 但是对于评论table你指定了条件comments.id=networks.comment_Id但是你忘记加入评论 table.

尝试

 SELECT networks.*, 
    products.product, 
    products.type, 
    comments.id AS comment_Id, 
    comments.newLine, 
    comments.lineComment AS comment, 
    comments.topComment, 
    comments.bottomComment 
    FROM products
    JOIN networks ON products.id=networks.product_Id
    JOIN comments ON comments.id=networks.comment_Id

MYSQL- select 并将多个表合并为一个 JSON

MYSQL- select and join multiple tables into one JSON

mysql

sql

select

join

multiple-tables