关于查询数据时出现的问题。

Question

在数据库中有一个学生信息表（student），一个成绩表（score），一个课程表（course）
我现在想进行如下操作：
1、做查询，显示四列：姓名，学号，课程名称，成绩，2、 课程表中有几个数据：数学，语文，英语。
    成绩表中有所有学生数学的成绩，其他课程成绩的没有（等待添加）。
    学生表中有所有学生的相关信息3、做查询时，前三列一定要显示内容，第四列（成绩）有数据的话就显示数据，没
   数据的就显示空。
以上要怎么写查询语句

Answer 1

表之间关联没有表述明白，假设学生表里有学生id studentid与score表里的sdid关联，
score里有subid与course表里的id关联
select student.姓名,student.学号,course.课程名称,isnull(cast (score.成绩 as varchar(20)),'') 成绩 from 
student inner join score
on student.studentid=score.sdid
inner join course
on score.subid=course.id

Answer 2

构造的一些数据
create table course
(
id int,
课程名称 varchar(255)
)
insert into course 
select 1,'数学' union all 
select 2,'语文' union all 
select 3,'英语'
create table student
(
studentid int,
姓名 varchar(255),
学号 varchar(10)
)
insert into student 
select 1,'张三','001' union all 
select 2,'李四','002'
create table score
(
sdid int,
成绩 int,
subid int
)
insert into score
select 1,80,1 union all
select 1,90,2 union all
select 1,60,3 union all
select 2,70,1 select b.姓名,b.学号,c.课程名称,isnull(cast(d.成绩 as varchar),'') 成绩
from 
(
select student.studentid,course.id from student cross join course
) a inner join student b on a.studentid=b.studentid
inner join course c on a.id=c.id
left outer join score d on a.studentid=d.sdid and a.id=d.subid
--结果
姓名                                                                                                                                                                                                                                                              学号         课程名称                                                                                                                                                                                                                                                            成绩
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------------------
张三                                                                                                                                                                                                                                                              001        数学                                                                                                                                                                                                                                                              80
张三                                                                                                                                                                                                                                                              001        语文                                                                                                                                                                                                                                                              90
张三                                                                                                                                                                                                                                                              001        英语                                                                                                                                                                                                                                                              60
李四                                                                                                                                                                                                                                                              002        数学                                                                                                                                                                                                                                                              70
李四                                                                                                                                                                                                                                                              002        语文                                                                                                                                                                                                                                                              
李四                                                                                                                                                                                                                                                              002        英语                                                                                                                                                                                                                                                              (6 行受影响)

Answer 3

hrb2008()   谢谢你的帮助，我自己也是这样做的
可是我接触的表不止这么几个 ，我写的那个连接语句 可以打印一张A4，
哪位大哥还有其他方法啊