Postgres:缺少表的FROM子句条目

Question

我正在尝试在postgres上为4个表执行连接查询.

表名:

• scenarios_scenario
• payments_invoice
• payments_payment
• payments_action

(所有这些奇怪的名字都是由django生成的 - )))

关系:

• scenarios_scenario[有很多] payments_actions
• payments_action [有一个] payments_invoice
• payments_action [有一个] payments_payment

下面是一个工作查询,

SELECT payments_invoice.*,
    (payments_payment.to_be_paid - payments_payment.paid) as remaining, \
    payments_action.identificator
FROM payments_invoice
JOIN payments_payment
  ON payments_invoice.action_id = payments_payment.action_id
  AND payments_payment.full_payment=2
JOIN payments_action
  ON payments_invoice.action_id = payments_action.id
  AND payments_action.identificator = %s

我只是想从另一个表中检索一个相关的字段,并写了另一个查询

SELECT 
  scenarios_scenario.title, payments_invoice.*, \
  (payments_payment.to_be_paid - payments_payment.paid) as remaining, \
  payments_action.identificator, payments_action.scenario_id 
FROM payments_invoice 
JOIN scenarios_scenario 
  ON scenarios_scenario.id = payments_action.scenario_id
JOIN payments_payment 
  ON payments_invoice.action_id = payments_payment.action_id 
  AND payments_payment.full_payment=2 
JOIN payments_action 
  ON payments_invoice.action_id = payments_action.id 
  AND payments_action.identificator = 'EEE45667';

但面对这个错误 -

ERROR:  missing FROM-clause entry for table "payments_action"
LINE 2: ...IN  scenarios_scenario ON scenarios_scenario.id = payments_a...
                                                             ^

在SO中查找类似的问题(缺少表格的FROM子句条目),但无法找到方法.任何帮助,将不胜感激.

Answer 1

在您的第一次加入中,"payments_action"不是已知的关系.以新连接仅使用已经"已定义"关系的方式重新排序连接.

这是一个小提琴,展示了这个问题:

http://sqlfiddle.com/#!17/ed147/5

Answer 2

更改代码，以使您先联接每个表，然后再在另一个联接中调用该表中的列。postgres查询计划程序按顺序读取联接，以便在您的代码表中将表scenarios_scenario联接到表中payments_invoice，并寻找与的匹配项payments_action，但查询计划程序尚不知道是什么payments_action。新代码应为：

SELECT 
    scenarios_scenario.title, payments_invoice.*, \
    (payments_payment.to_be_paid - payments_payment.paid) as remaining, \
    payments_action.identificator, payments_action.scenario_id 
FROM payments_invoice 
JOIN payments_action 
ON (
    payments_invoice.action_id = payments_action.id 
    AND payments_action.identificator = 'EEE45667'    
)
JOIN scenarios_scenario 
ON (
    scenarios_scenario.id = payments_action.scenario_id
)
JOIN payments_payment 
ON (
    payments_invoice.action_id = payments_payment.action_id 
    AND payments_payment.full_payment=2 
);

Answer 3

您正在使用 [payments_action] 中的字段加入表 [scenarios_scenario]。

连接必须按顺序进行，即您不能使用 ON 语句引用表中的字段，除非它们的表在语句之前。

希望有帮助