mysql - 从 2 个表中选择。 MySql

Question

如何在不输入长全名的情况下选择 p.Quota？现在我正在做

SELECT c.id, 
       c.UserName, 
       p.Quota, 
       cs.StatusName 
  FROM CUSTOMERS AS c, 
       PRODUCTS AS p 
 LEFT JOIN CUSTOMERSTATUSTYPES as cs ON c.StatusId=cs.CustomerStatusId 
 LIMIT 1 ;

我得到错误:

ERROR 1054 (42S22): Unknown column 'c.StatusId' in 'on clause'

但是该列确实退出并且此代码有效:

SELECT c.id, 
       c.UserName, 
       cs.StatusName 
  FROM CUSTOMERS AS c
  JOIN CUSTOMERSTATUSTYPES as cs ON c.StatusId = cs.CustomerStatusId 
 LIMIT 1 ;

Answer 1

您正在混合使用 ANSI 和非 ANSI JOIN 语法:

SELECT c.id, 
       c.UserName, 
       p.Quota, 
       cs.StatusName 
  FROM CUSTOMERS AS c, 
       PRODUCTS AS p 
  LEFT JOIN CUSTOMERSTATUSTYPES as cs ON c.StatusId=cs.CustomerStatusId 
  LIMIT 1 ;

使用 ANSI 连接编写:

     SELECT c.id, 
            c.UserName, 
            p.Quota, 
            cs.StatusName 
       FROM CUSTOMERS AS c 
       JOIN PRODUCTS AS p ON --JOIN criteria goes here
  LEFT JOIN CUSTOMERSTATUSTYPES as cs ON c.StatusId = cs.CustomerStatusId 
      LIMIT 1;

...但我不知道您使用什么标准将 PRODUCTS 加入 CUSTOMERS 表。