如何限制LEFT JOIN？

Question

我制作了两张这样的表

degree_plan                              student_record
------------------------------      ----------------------------
major    course     course_no        ID       course_no     grade        
------------------------------      ----------------------------
COE      COE200        1             4455        1           A
COE      COE305        2             4455        2           C
COE      COE400        3             3333        4           B
SWE      SWE214        4
SWE      SWE344        5
SWE      SWE444        6

course_no是表格之间的关系

如何在SQL中编写查询以便像我这样where ID=4455 and the major = COE

--------------------------
major   course       grade
--------------------------
COE     COE200        A
COE     COE305        C
COE     COE400        NULL

Answer 1

select * 
from degree_plan 
left join studen`t_record 
on studen`t_record.course_no = degree_plan.course_no 
where major = 'COE'

你需要在哪里过滤

Answer 2

试试这个：

select a.major, a.course, b.grade
from degree_plan a
left join studen`t_record b on b.course_no = a.course_no
where a.major = 'COE'

你甚至不需要喜欢条款，因为主要领域不长于COE

Answer 3

试试这种方式

select a.mjor, a.course, b.grade 
from degree_plan as a
left join student_record as b on a.course_no=b.course_no and b.id=4455
where a.major='COE'

Answer 4

   SELECT degree_plan.major, degree_plan.course, studen't_record.grade 
     FROM degree_plan
LEFT JOIN Student_record ON degree_plan.course_no=student_record.course_no where degree.major='COE';