空结果SQL查询。 [英] Empty result SQL query.

问题描述

我正在尝试从表std_details中检索StudentID，FirstName，LastName和CGPA，这取决于学生采用set模块的条件。这是我设计的querry，不幸的是它返回并且空集：

Hi,
I'm trying to retreive the StudentID, FirstName, LastName and CGPA from the table std_details this based on the condition that the student takes a set module. Here is the querry that I designed unfortunately it return and empty set:

SELECT 
	std_details.StudentID, 
	std_details.FirstName, 
	std_details.LastName, 
	std_details.CGPA 
FROM std_details 
INNER JOIN csr_courses 
	ON std_details.StudentID = csr_courses.StudentID 
WHERE csr_courses.Course_1 = 'PHIL340' 
OR csr_courses.Course_2 = 'PHIL340' 
OR csr_courses.Course_3 = 'PHIL340' 
OR csr_courses.Course_4 = 'PHIL340' 
OR csr_courses.Course_5 = 'PHIL340'
;

我不确定我是否正在加入，我对sql很新。



这是csr表的一些示例数据：

http://hpics.li/bd9a863





和标准表格：

http ：//hpics.li/13384e0



确切的错误代码是：

I'm not sure I'm doing the Join right, I'm quite new to sql.

Here is some sample data for the csr table:
http://hpics.li/bd9a863


and fort the std table:
http://hpics.li/13384e0

The exact error code is:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INNER JOIN csr_courses ON std_details.StudentID = csr_courses.StudentIDWHERE csr' at line 1

推荐答案

您需要使用别名+ RIGHT JOIN，这意味着：从 csr_courses 获取所有记录并匹配来自 std_details的数据：

You need to use aliases + RIGHT JOIN, which means: get all records from csr_courses and matching data from std_details:

SELECT sd.StudentID, sd.FirstName, sd.LastName, sd.CGPA
FROM std_details sd RIGHT JOIN csr_courses cc ON sd.StudentID = cc.StudentID
WHERE cc.Course_1 = 'PHIL340' OR cc.Course_2 = 'PHIL340' OR cc.Course_3 = 'PHIL340' OR cc.Course_4 = 'PHIL340' OR cc.Course_5 = 'PHIL340'

详情请见：

SQL连接的可视化表示 [ ^ ]

MySQL JOIN [ ^ ]



顺便说一下：你确定 csr_courses 包含在中搜索数据Course_x 字段？

For further information, please see:
Visual Representation of SQL Joins[^]
MySQL JOIN[^]

By The Way: Are you sure that csr_courses contains searched data in Course_x field?

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