Question

我是SQL的新手，需要一些帮助。在一个场景中，我想加入教师表，在那里我有老师教授的主题数据。我想通过连接添加一些缺失的行，这样我就可以显示一年中教授课程的行，但却缺少教师的详细信息。无论是在所有科目的任何学期。

注意可能有多个没有。一年内的术语

他们认为的教师和班级的映射表

Teacher Class
Aman    9th
Ankit   9th
Abhinav 10th
Bharat  10th

教师的映射表和他们认为的术语

Teacher Term
Aman    1stTerm
Ankit   2nd Term
Abhinav 2nd Term
Bharat  1stTerm

数据表

Subject YEAR    Teacher Marks
Maths   2014    Aman    80
Maths   2014    Ankit   85
Maths   2015    Abhinav 69
Science 2014    Abhinav 30
Science 2015    Aman    20

输出表

Subject Class   Teacher Class   Term        Marks
Maths   2014    Aman    9th     1stTerm     80
Maths   2014    Ankit   9th     2nd Term    85
Maths   2015    Abhinav 10th    2nd Term    69
Maths   2015    Bharat  10th    1stTerm     0
Science 2014    Abhinav 10th    2nd Term    30
Science 2014    Bharat  10th    1stTerm     0
Science 2015    Aman    9th     1stTerm     20
Science 2015    Ankit   9th     2nd Term    0

Answer 1

我现在无法检查，但这样的事情应该有效：

select *, coalesce(dt.Marks, 0) as Marks
from TeacherClass tc
join TeacherTerm tt on tc.Teacher = tt.Teacher
cross join (select 2014 as Year union select 2015 as Year) cj
left join DataTable dt on tc.Teacher = dt.Teacher and cj.Year = dt.Year



DECLARE @TeacherClass TABLE(Teacher VARCHAR(MAX), Class VARCHAR(MAX))
DECLARE @TeacherTerm TABLE(Teacher VARCHAR(MAX), Term VARCHAR(MAX))
DECLARE @DataTable TABLE(Subject VARCHAR(MAX), YEAR  INT,   Teacher VARCHAR(MAX), Marks INT)


INSERT INTO @TeacherClass VALUES
('Aman','9th'),
('Ankit','9th'),
('Abhinav','10th'),
('Bharat','10th')

INSERT INTO @TeacherTerm VALUES
('Aman','1stTerm'),
('Ankit','2nd Term'),
('Abhinav','2nd Term'),
('Bharat','1stTerm')

INSERT INTO @DataTable VALUES
('Maths',   2014    ,'Aman',    80),
('Maths',   2014    ,'Ankit',   85),
('Maths',   2015    ,'Abhinav', 69),
('Science', 2014    ,'Abhinav', 30),
('Science', 2015    ,'Aman',    20)


select Subject, cj.Year, tc.Teacher, tc.Class, tt.Term, coalesce(dt.Marks, 0) as Marks
from @TeacherClass tc
join @TeacherTerm tt on tc.Teacher = tt.Teacher
cross join (select 2014 as Year union select 2015 as Year) cj
left join @DataTable dt on tc.Teacher = dt.Teacher and cj.Year = dt.Year
ORDER BY Subject, cj.YEAR

输出：

Subject Year    Teacher Class   Term        Marks
NULL    2014    Bharat  10th    1stTerm     0
NULL    2015    Bharat  10th    1stTerm     0
NULL    2015    Ankit   9th     2nd Term    0
Maths   2014    Aman    9th     1stTerm     80
Maths   2014    Ankit   9th     2nd Term    85
Maths   2015    Abhinav 10th    2nd Term    69
Science 2014    Abhinav 10th    2nd Term    30
Science 2015    Aman    9th     1stTerm     20

SQL连接添加缺少的行

1 个答案: