Mysql 使用 LEFT JOIN 没有结果时出现 Column cannot be null 错误

Question

我在客户 table 中有一些数据，而在其他 table 中没有数据。因此，当我尝试 select 使用以下查询时，它给了我

1048-Column 'customerid' cannot be null

。可能是什么问题呢。有解决办法吗？

SELECT c.*, fd.ruakzat as ruak,
        fd.khatzat as khat, 0+0 as belh, 0+0 as neih, 
        puk.lended as hawh
        FROM `customer` c
        LEFT JOIN ( 
                SELECT s.customerid, o.orderzat as ruakzat, 
                       f.filled as khatzat     
                FROM `sale` s    
                LEFT JOIN (     
                       SELECT SUM(quantity) as orderzat,invoiceno     
                       FROM `order`    
                       WHERE fillstatus='Empty'
                       GROUP BY invoiceno    
                 ) AS o ON s.invoiceno=o.invoiceno    
                LEFT JOIN (     
                      SELECT SUM(quantity) as filled,invoiceno    
                      FROM `order`    
                      WHERE fillstatus='Filled'    
                      GROUP BY invoiceno    
                ) AS f ON s.invoiceno=f.invoiceno    
        ) AS fd ON c.id=fd.customerid    
        LEFT JOIN (     
             SELECT SUM(quantity) as lended, customerid    
             FROM `lending`    
        ) AS puk ON c.id=puk.customerid     
       WHERE (puk.customerid IS NULL OR c.name LIKE '%%')

更好的方法是什么？感谢您的帮助。

Answer 1

MySQL 有一些关于类似问题的错误报告 (https://bugs.mysql.com/bug.php?id=31450 , https://bugs.mysql.com/bug.php?id=35633 , https://bugs.mysql.com/bug.php?id=52441)，因此您可能遇到了相同的错误。

总结一下：如果相关字段根据定义是不可空的（在创建 table 中定义为非空），但出现在输出结果可能为空的子查询中。

请检查您的 MySQL 版本，因为该版本可能确实出现了上面列出的错误之一。

此外，对我来说子查询

         SELECT SUM(quantity) as lended, customerid    
         FROM `lending`

没有太大意义，因为没有按部分分组。这会将贷款 table 合并为一条记录，并从其中一条记录中随机选择 customerid。所以，我会在上面的子查询中添加一个 group by customerid。

Answer 2

与你的问题无关，但你可以替换那两个join

        LEFT JOIN (     
               SELECT SUM(quantity) as orderzat,invoiceno     
               FROM `order`    
               WHERE fillstatus='Empty'
               GROUP BY invoiceno    
         ) AS o ON s.invoiceno=o.invoiceno    
        LEFT JOIN (     
              SELECT SUM(quantity) as filled,invoiceno    
              FROM `order`    
              WHERE fillstatus='Filled'    
              GROUP BY invoiceno

一个使用 Conditional SUM

        LEFT JOIN (     
               SELECT invoiceno, 
                      SUM(CASE WHEN fillstatus='Empty' THEN quantity
                                                       ELSE 0
                          END) as orderzat,     
                      SUM(CASE WHEN fillstatus='Filled' THEN quantity
                                                        ELSE 0
                          END) as filled     
               FROM `order`    
               GROUP BY invoiceno    
         ) AS o ON s.invoiceno=o.invoiceno

Mysql 使用 LEFT JOIN 没有结果时出现 Column cannot be null 错误

Mysql Column cannot be null error when there is no result using LEFT JOIN

mysql

sql

subquery

left-join

1048-Column 'customerid' cannot be null