Question

很抱歉，如果这个问题看起来很奇怪，但我正在尝试在SQL中加入一些表，我无法做到正确。我是新手，所以，如果你想解释我做错了什么，我会非常感激。

基本上，我要做的是加入以下表格：会议，用户和服务。用户可以是主持人或管理员，并且该信息在设置列中定义。我希望INNER JOIN moderator_id与users.id WHERE users.settings =＆＃39;主持人＆＃39;还有INNER JOIN admin_id和users.id WHERE users.settings =＆＃39; admin＆＃39;。

希望你们明白我要做的事情：）

谢谢！

SELECT meetings.*
     , users.id
     , users.name
     , users.settings
     , services.id
     , services.service_name
     , services.price 
  FROM meetings 
  JOIN users 
    ON meetings.moderator_id = users.id 
 WHERE users.settings = 'moderator' 
  JOIN users 
    ON meetings.admin_id = users.id 
 WHERE users.settings = 'admin' 
  JOIN services 
    ON meetings.service_id = services.id 
 ORDER 
    BY meetings.date ASC

Answer 1

SELECT meetings.*, users.id, users.name, users.settings, services.id, services.service_name, services.price 
FROM meetings

INNER JOIN users as mods ON meetings.moderator_id = mods.id 
INNER JOIN users as adms ON meetings.admin_id = adms.id
INNER JOIN services ON meetings.service_id = services.id

WHERE adms.users.settings = 'admin' AND mods.users.settings = 'moderator' 
ORDER BY appointments.date ASC

我猜你需要为admins和moderatores指定用户实例，然后在连接后放置where。试试这个查询并告诉我它是否有效。

Answer 2

SELECT的语法是：

SELECT <fields>
FROM <table>
JOIN <table> ON <condition>
JOIN <table> ON <condition>
...
WHERE <condition> AND <condition> AND ...
ORDER BY <column>, <column>, ...

即。列出所涉及的所有表，然后列出条件。这是SQL查询的一般结构，所以随意记住它:)。另请注意，这当然是极端简化，还有更多内容。（例如，在WHERE子句中使用OR代替AND，但这是另一个故事。）祝你好运。

编辑：如果别名表，例如“FROM tablename AS newtablename”，则应使用别名newtablename作为WHERE中的条件，SELECT中的列等。否则，您将收到有关无法找到的内容的消息。您可以在查询期间重命名表，并抛弃旧名称。

Answer 3

E.g：

SELECT m.*
     , mods.name mod_name
     , admins.name admin_name
     , s.service_name
     , s.price 
  FROM meetings m
  JOIN users mods
    ON mods.id = m.moderator_id 
  JOIN users admins
    ON admins.id = m.admin_id
  JOIN services s
    ON s.id = m.service_id 
 WHERE mods.settings = 'moderator' 
   AND admins.settings = 'admin';

...或者，更有可能......

SELECT m.*
     , mods.name mod_name
     , admins.name admin_name
     , s.service_name
     , s.price 
  FROM meetings m
  LEFT
  JOIN users mods
    ON mods.id = m.moderator_id 
   AND mods.settings = 'moderator' 
  LEFT
  JOIN users admins
    ON admins.id = m.admin_id
   AND admins.settings = 'admin'
  JOIN services s
    ON s.id = m.service_id;

Answer 4

我通过结合你的一些建议找到了答案！它现在似乎工作得很好，所以谢谢你们的帮助！

SELECT meetings.*, 
  mods.id, 
  mods.name as mods_name, 
  mods.settings, 
  admins.id, 
  admins.name as admins_name, 
  admins.settings, 
  services.id, 
  services.service_name, 
  services.price

FROM meetings 

INNER JOIN users as mods ON meetings.moderator_id = mods.id 
INNER JOIN users as admins ON meetings.admin_id = admins.id
INNER JOIN services ON meetings.service_id = services.id

WHERE mods.settings = 'moderator' AND admins.settings = 'admin' 
ORDER BY meetings.date ASC

MySQL INNER加入3个与WHERE

4 个答案: