带有GROUP BY和WHERE子句的INNER JOIN错误 [英] Error for INNER JOIN with GROUP BY and WHERE clause

问题描述

我有这些桌子

学生：

id  Name
-------------------
1   john
2   carlos
3   zoya
4   arab
5   amir

以及

电子邮件：

id      email   student_id
--------------------------
1   [e-mail]      1
2   [e-mail]      2
3   [e-mail]      2
4   [e-mail]      3
5   [e-mail]      4

我正在使用此查询，并且在查询第4行上使用sql错误，

I'm using this query and it's getting Using sql error on query line 4,

SELECT * FROM student 
INNER JOIN email 
ON student.id = email.student_id 
GROUP BY student.id
WHERE student.id = 2

我在SQL方面没有太多经验。

I don't have much experience in SQL.

推荐答案

首先， GROUP BY 总是放在 WHERE 子句。

其次，i如果您正在使用 GROUP BY 子句，则应该对字段使用聚合函数，这些函数不包含在其中，但仍存在于 SELECT中子句，或 GROUP BY 包含在 SELECT 中的整个列包。

Firstly, GROUP BY always goes after the WHERE clause.
Secondly, if you are using the GROUP BY clause you should either use aggregate functions for the fields, that are not contained in it and still are present in the SELECT clause, or GROUP BY the whole pack of columns contained in the SELECT.

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