从 mysql 数据库中选择多表（在单个字段中返回多个项目）

Question

我需要一些认真的帮助。事情是这样的... 假设我有一个带有字段（userId，name）的“用户”表。现在我需要从与该用户相关的其他表中获取多项信息。有些物品相似，所以需要捆绑在一起。

现在我还有其他几个表：

CREATE TABLE app.phones (
`id` INT NOT NULL AUTO_INCREMENT ,
`userId` INT NOT NULL ,
`phone` VARCHAR( 16 ) NOT NULL ,
PRIMARY KEY ( `id` )
) ENGINE = InnoDB;

CREATE TABLE app.emails (
`id` INT NOT NULL AUTO_INCREMENT ,
`userId` INT NOT NULL ,
`email` VARCHAR( 32 ) NOT NULL ,
PRIMARY KEY ( `id` )
) ENGINE = InnoDB;

CREATE TABLE app.contact_methods (
`id` INT NOT NULL AUTO_INCREMENT ,
`userId` INT NOT NULL ,
`method` ENUM( 'phone', 'email' ) NOT NULL,
`methodId` INT NOT NULL ,
PRIMARY KEY ( `id` )
) ENGINE = InnoDB;

CREATE TABLE app.groups (
`id` INT NOT NULL AUTO_INCREMENT ,
`groupName` VARCHAR( 16 ) NOT NULL ,
PRIMARY KEY ( `id` )
) ENGINE = InnoDB;

CREATE TABLE app.users_groups (
`id` INT NOT NULL AUTO_INCREMENT ,
`userId` INT NOT NULL ,
`groupId` INT NOT NULL ,
PRIMARY KEY ( `id` )
) ENGINE = InnoDB;

您可能已经猜到，每个用户都可以拥有多封电子邮件、多部电话并属于多个群组。如何使用上面的所有表格显示如下表格？

+---------+-------------+-------------------+--------------+
|name     |phones       |emails             |groups        |
+---------+-------------+-------------------+--------------+
|John Doe |123-555-0101,|johndoe@mail.com,  |group1,group2,|
|         |123-555-0909 |johndoe2@mail.com  |group3        |
+---------+-------------+---------+---------+--------------+

更新：电子邮件和电话不应立即从他们的桌子上拿走。表 contact_methods 包含引用这些表的条目。

Answer 1

试试这个尺寸

SELECT u.name, ph.phone, em.email, gr.groupName 
FROM users AS u, phones AS ph, emails AS em, groups AS gr 
WHERE (u.id = ph.userId) 
    AND (u.id = em.userId) 
    AND (u.id = gr.userId) 
GROUP BY u.id

或者将值连接起来得到一行（感谢@chris-morgan）：

SELECT u.name, 
    GROUP_CONCAT(ph.phone SEPARATOR ','), 
    GROUP_CONCAT(em.email SEPARATOR ','), 
    GROUP_CONCAT(gr.groupName SEPARATOR ',') 
FROM users AS u, phones AS ph, emails AS em, groups AS gr 
WHERE (u.id = ph.userId) 
    AND (u.id = em.userId) 
    AND (u.id = gr.userId) 
GROUP BY u.id