Question

我这里有一个复杂的查询。我必须按名称选择列，不能只是用户'订单。*。因为我有来自不同表的多个具有相同名称的列。

我尝试做的是仅在订单，用户，payment_methods_translation中选择特定字段，并且仅在orders.payment_method_id ='3'

时才加入bank_accounts_translation

SELECT 
   orders.id as orderid,
   orders.final_total,
   orders.user_id,
   orders.auto_cancel,
   users.id as userid,
   users.first_name,
   payment_methods_translation.payment_method_id,
   payment_methods_translation.name 
FROM 
   orders,users, 
   payment_methods_translation
WHERE
   orders.id='$id' AND 
   orders.user_id = users.id AND
   orders.payment_method_id = payment_methods_translation.payment_method_id AND 
   orders.auto_cancel='1' 
JOIN 
   bank_accounts_translation ON (orders.payment_method_id='3' 
   AND orders.bank_id = bank_accounts_translation.bank_account_id)

但是我收到了一个mysql错误。那么，如果orders.payment_method_id ='3'和orders.bank_id = bank_accounts_translation.bank_id

，我怎样才能从bank_accounts_translation中选择所有字段

Answer 1

左连接应该这样做......我

重构代码以使用当前的ANSI标准，您似乎正在混合它们。
使用表别名来提高可读性。

LEFT JOIN表示返回先前列出的表中的所有记录，并且仅返回与要加入的表的on标准匹配的记录。

SELECT O.id as orderid
      ,O.final_total
      ,O.user_id
      ,O.auto_cancel
      ,u.id as userid
      ,u.first_name
      ,PMT.payment_method_id
      ,PMT.name 
FROM orders O
INNER JOIN users U
   ON O.user_id = U.id 
INNER JOIN payment_methods_translation  PMT
   ON O.payment_method_id = PMT.payment_method_id 
LEFT JOIN bank_accounts_translation  BAT
   ON O.payment_method_id='3' 
  and O.bank_id = BAT.bank_account_id
WHERE O.id='$id' 
  and O.auto_cancel='1'

只有当MySQL将表连接到另一个表时

1 个答案: