如何使用SQL连接从两个表中选择表

Question

I have to table in SQL course and student

Course table has following fields

courseid coursename courseduration

Student table has the following fields

rollno  name  address courseid 

I want the result as following

 BCA
   abc
   def
   pqr
 MCA
   stu
   ijk
 BTECH
   xyz

I am applying inner join for it like following suggest me query for desired result My query is following:

SELECT student.name
FROM student
INNER JOIN course
ON student.courseid=course.courseid;

Answer 1

You can try this:

SELECT 
  course.name AS course_name, 
  GROUP_CONCAT(student.name) AS student_name
FROM student
INNER JOIN course
ON student.courseid = course.courseid
GROUP BY course.courseid;

This will give you something like this:

Course_name   |  Student_name
BCA           |  abc,def,pqr
MCA           |  stu,ijk
BTECH         |  xyz

Answer 2

Here are some options

1) Include the course name in the select and order by it - it will be repeated on each row for the student in the course

SELECT course.name, student.name
FROM student
INNER JOIN course
ON student.courseid=course.courseid
ORDER BY course.name;

Which will return

Course Student
 BCA   abc
 BCA   def
 BCA   pqr
 MCA   stu
 MCA   ijk
 BTECH  xyz

You would do the indentation in your presentation tier, eg by indenting every time the course name changes.

2) You can use GROUP_CONCAT to combine all students into a single column for a grouping on Course_name

SELECT course.name, GROUP_CONCAT(student.name) AS Students
FROM student
INNER JOIN course
ON student.courseid=course.courseid
GROUP BY course.name;

Returns

 Course  Students
 BCA     abc, def, pqr
 MCA     stu, ijk
 BTECH   xyz

Edit, re I just want one column

Well, you can project and combine the course name and student names with a UNION into a single column, and use an ordering hack to associate the students like this . In fact, you can even add spaces to get the indentation effect. But this is solving the wrong problem - this kind of formatting is presentation tier and shouldn't be done in Sql IMO.

SELECT Name
FROM
(
  SELECT course.coursename AS Name, course.coursename AS Course, 1 As RowType
  FROM course

  UNION ALL

  SELECT CONCAT('   ', student.name), course.coursename, 2 AS RowType
  FROM student
  INNER JOIN course
  ON student.courseid=course.courseid
) x
ORDER BY Course, RowType;

Returns

BCA
 abc
 def
 pqr
BTECH
 xyz
MCA
 ijk
 stu

Answer 3

Try this

SELECT `name`
FROM(
SELECT course.courseid, course.coursename AS `name`
FROM course
UNION
SELECT student.courseid + 0.1 AS courseid, courseid.name AS `name`
FROM student
ORDER BY courseid ASC) AS ordered_list