There are three tables
Student (STUDID, NAME, AGE, ADDRESS)
Course (COURSEID, COURSENAME, CREDIT)
Student_Course (SCID, STUDID, COURSEID)
How to show the total credits registered by one particular student id?
Here's the details about the tables
You should use JOIN , SUM() and group by
select a.STUDID, a.NAME, sum(b.CREDIT)
from Student a
inner join Student_Course c on a.STUDID = c.STUDID
inner join Course b on c.COURSEID = b.COURSEID
group by a.STUDID, a.NAME
Related
Using SQL, my job is to fetch the SSN of students who enrolled in a course without enrolling in that course’s prerequisite(s). I'm using Access. The tables I need are as follows:
STUDENT (SSN, SNAME, MAJOR, DOB, ADDRESS)
ENROLLED (SSN, CID, GRADE)
PREQ (CID, PREQCID, PASSINGGRADE, NOTE)
Here's what I've done so far.
select *
from
(select SSN, CID from ENROLLED) AS enrolled
left join
(select CID, PREQCID FROM PREQ) AS prereq ON enrolled.CID = prereq.CID;
What I'm missing is how to check each row of the same student on the condition WHERE enrolled.CID = prereq.CID for a PREQCID that's NOT in enrolled.CID.
Is what I'm asking for here a loop? Am I on the right track? Please keep in mind this I'm in an introductory course so the simplest of solutions is preferable.
Here's another way using not exists:
select e1.ssn
from enrolled e1 left join preq p on e1.cid = p.cid
where
p.preqcid is not null and
not exists (select 1 from enrolled e2 where e2.ssn = e1.ssn and e2.cid = p.preqcid)
This is essentially stating:
"Select the ssn for all enrollments where there is a prerequisite course and the prerequisite course ID does not exist in the table of enrollments for that ssn."
I use select 1 purely for optimisation - we don't care about the values held by the nested query, only whether or not the nested query returns one or more records.
You could also write this using joins as:
select e1.ssn
from
(
enrolled e1 left join preq p on e1.cid = p.cid
)
left join enrolled e2 on
p.preqcid = e2.cid and e1.ssn = e2.ssn
where
e2.cid is null
Here, the enrolled table is referenced twice: the first is left joined on the table of prerequisite courses for each course, and the second is left joined on the prerequisite course ID and the ssn from the original enrollment.
The where clause then causes records to be selected for which the link on the prerequisite course is null for the given ssn.
I'm sure there is a cleaner way to do this, but this gets you your result:
Select S.SSN, E.CID From Student S
Inner Join Enrolled E on E.SSN = S.SSN
Where E.CID IN (Select CID From PREQ Where Preqcid NOT IN
(Select CID From Enbrolled Where SSN = S.SSN))
This might work if analytic functions and CTEs are available:
with d as (
select ssn, cid,
count(distinct p.cid) over (partition by e.ssn, e.cid) ecnt, ,
count(distinct e.cid) over (partition by e.ssn, p.cid) pcnt
from enrolled e left outer join preq p on p.cid = e.cid
)
select distinct ssn, cid from d
where ecnt = pcnt;
select s.name, s.id
from student s join takes t on t.id = s.id
where s.name like 'D%'
group by s.name, s.id
having (
select count(distinct c.course_id)
from course c
where c.dept_name = 'History' and c.course_id = t.course_id)>4
order by s.name
I am confused about how GROUP BY works. I am trying to find the students who has taken at least 5 courses from history department and name start with D.
Not sure with the nested subqueries...
course(course id, title, dept name, credits)
student(ID, name, dept name, tot_cred)
takes(ID, course_id, sec_id, semester, year, grade)
You have to additionally JOIN with course table:
select s.name, s.id
from student s
inner join takes t on t.id = s.id
inner join course c on c.course_id = t.course_id
where s.name like 'D%' and c.dept_name = 'History'
group by s.name, s.id
having count(distinct c.course_id) >= 5
The WHERE clause returns all students whose names start with a 'D' and have taken at least one course in history department. The HAVING clause filters out any students with 4 or less distinct courses in history department.
I have a simple problem but I want to use Not having. I have two tables: student_table, and student_course
STUDENT (
ID,
Name
)
STUDENT_COURSE (
ID,
student_ID,
course_ID
)
I want to select those student name that does not have any corresponding course_ID in the STUDENT_COURSE table, so I write
SELECT *
FROM STUDENT
LEFT JOIN STUDENT_COURSE ON STUDENT_COURSE.STUDENT_ID = STUDENT.ID
but how can I write Not having in the next?
To find STUDENT with no STUDENT_COURSE, you could use different methods. See this article for the comparisons:
using NOT EXISTS:
SELECT s.*
FROM STUDENT s
WHERE NOT EXISTS(
SELECT 1 FROM STUDENT_COURSE c WHERE c.STUDENT_ID = s.ID
)
using LEFT JOIN
SELECT
s.*
FROM STUDENT s
LEFT JOIN STUDENT_COURSE c
ON c.STUDENT_ID = s.ID
WHERE c.ID IS NULL
using NOT IN
SELECT *
FROM STUDENT
WHERE ID NOT IN(
SELECT STUDENT_ID FROM STUDENT_COURSE
)
Just Add [STUDENT_COURSE].[STUDENT_ID] IS NULL filter which will find the students not invloved in any course
Left Outer join will produce NULL values for the right table columns which don't have a match.
SELECT *
FROM [STUDENT]
LEFT JOIN [STUDENT_COURSE]
ON [STUDENT_COURSE].[STUDENT_ID] = STUDENT.ID
WHERE [STUDENT_COURSE].[STUDENT_ID] IS NULL
Consider the following schema for SQL:
Student (StudID, StudName, DeptID, Age, Gpa);
Course (CourseID, CourseName, InstructorID);
Department (DeptID, DeptName, Location);
Instructor (InstructorID, InstructorName, DeptID);
Section (SectionID, SectionName, Time, RoomID, CourseID, InstructorID);
Room (RoomID, RoomName, Location);
Enrolled (StudID, SectionID);
Q: How to find the names of all sections that either meet in common room or have five or more students enrolled?
Well I am not sure if it will work:)
Common names;
select st.StudName as names from Student as st inner join Departmant as d
on st.DeptID = d.DeptID inner join Instructor as i
on i.DeptID = d.DeptID inner join Course as c
on c.InstructorID = i.InstructorID inner join Section as s
on s.InstructorID = i.InstructorID inner join Room as r
on r.RoomID = s.RoomID inner join Enrolled as e
on e.StudID = st.StudID;
More than 5 student enrolled(Something experimental:);
select st.StudName as names from Student as st inner join Departmant as d
on st.DeptID = d.DeptID inner join Instructor as i
on i.DeptID = d.DeptID inner join Course as c
on c.InstructorID = i.InstructorID inner join Section as s
on s.InstructorID = i.InstructorID inner join Room as r
on r.RoomID = s.RoomID inner join Enrolled as e
on e.StudID = st.StudID where count(e.StudID = st.StudID)>4;
If you are using SQL-Server you can write the query like this(I didn't tested it. So I can't say it works 100% but I hope it gives you an idea):
SELECT SectionName
FROM Section
WHERE SectionID IN --Students in common room.
(
SELECT SectionID FROM Section
INNER JOIN Instructor ON Section.SectionID = Instructor.InstructorID --Section to which the Instructor belongs
INNER JOIN Department ON Department.DeptID = Instructor.DeptID --Department to which the Instructor belongs
INNER JOIN Room ON Room.Location = Department.Location --Room to which the Department belongs
)
OR --Student Enrollment greater than 5.
(
(SELECT COUNT(StudID) FROM Student
INNER JOIN Enrolled ON Student.StudID = Enrolled.StudID
INNER JOIN Section ON Section.SectionID = Enrolled.SectionID) >= 5
)
Q:6. Find the names of all sections that either meet in room New-8 or have five or more students enrolled.
Answer:
select sectionName
from student as S, Enrolled as E, Section as Se
where S.studId=E.studId AND E.sectionID=se.SectionID
group by sectionName
having count(*)>=3
UNION
SELECT sectionName
FROM SECTION S, ROOM R
WHERE S.RoomID=R.ROOMID AND R.RoomName='new2'
this is the correct query i have run it on Db
This is a question I could not answer in oracle lab exam.
Given the schema:
(Courses: cid(int), deptid(int)...);
(Students: sid(int), sname (string), deptid(int)...);
(Participation: cid(int), sid(int), ...);
A student can attend courses outside his department.
Need to get the names of the students who take all the courses offered by his department.
How to do this in sqlplus?
SELECT s.sid, s.sname, s.deptid
FROM Students s
INNER JOIN Participation p
ON s.sid = p.sid
INNER JOIN Courses c
ON p.cid = c.cid
AND s.deptid = c.deptid
GROUP BY s.sid, s.sname, s.deptid
HAVING COUNT(DISTINCT c.cid) = (SELECT COUNT(*)
FROM Courses c2
WHERE c2.deptid = s.deptid)
I cannot tesst the query right now, so I don't know if I have a syntactic error, anyway, you can try this idea to achieve your requirements.
SELECT studentName
FROM
(SELECT stu.sname AS studentName,
cour.deptid AS dept,
COUNT(*) AS assistedCoursesByDpt,
Max(cour.total) AS total
FROM students stu,
participation part,
(SELECT cour.deptid,COUNT(*) AS total FROM courses cour GROUP BY cour.deptid
) AS cour
WHERE stu.sid=part.sid
AND part.cid =cour.cid
GROUP BY stu.sid,
cour.deptid
)
WHERE total=assistedCoursesByDpt
Th idea is to create a subquery (cour) that has a new calculated column, the total courses by debt. Then you can compare this total with the agrouped student courses by dept.