如何编写一个MySQL查询来获取PHP中的二维表？

Question

I am trying to output a 2D table in php but not able to figure out the sql query for the same

My tables are as below

Students
========
ID | Name
1  | Student1
2  | Student2
3  | Student3

Projects
========
ID | Name
1  | Project1
2  | Project2
3  | Project3

Timesheet
========
ID | Project_id | Student_id | hours
1  | 1          | 1          | 2.5
2  | 2          | 2          | 3
3  | 2          | 1          | 4.5
4  | 1          | 3          | 5
5  | 3          | 3          | 2
6  | 3          | 2          | 1
7  | 3          | 3          | 3.5
8  | 2          | 1          | 6

I want the output as below

           | Student1 | Student2 | Student3
Project1   |    2.5   |    0     |   5
Project2   |   10.5   |    3     |   0
Project3   |     0    |    1     |   5.5

Number of students and project will increase and not constant. Is it possible to write in one sql join query or do I have to write multiple nested php loops to get the above output?

Answer 1

For a big dataset, complex queries using multiple JOINs are basically not good.

"SELECT SUM(hours) AS total FROM Timesheet GROUP BY Project_id, Student_id"

"SELECT ID,Name FROM Students"

"SELECT ID,Name FROM Projects"

I'd rather execute 3 simple queries, then match student and project names in a single loop