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Basic Join Problem

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Basic Join Problem Oracle Development forum discussing administration, Oracle queries, and other Oracle-related topics. Oracle is known as one of the most robust multi-platform relational databases available.

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  #1  
Old April 20th, 2008, 03:14 PM
buster.t buster.t is offline
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Basic Join Problem
Hello,

I am not very experienced with SQL. I apologize if this is trivial. I have two tables:

Class
-----
ID (int)
Teacher (nvarchar)
Subject (nvarchar)

Student
--------
ID (int)
ClassID (int)
Name (nvarchar)

I am trying to write a SQL query that will give me the total number of students in each class. I have tried the following:

SELECT
c.ID,
c.Teacher,
c.Subject
COUNT(s.ID)
FROM
Class c LEFT OUTER JOINT ON Student s c.ID=s.ClassID

Unfortunately, that gives me an error of:
Column 'Class.Teacher' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

I'm afraid if I place everything in a GROUP BY clause, I will get some invalid results.

Can anyone please steer me in the correct direction?

Thank you!
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  #2  
Old April 20th, 2008, 04:38 PM
swampBoogie swampBoogie is offline
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Put all selected columns, except s.id, in the group by clause.
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  #3  
Old April 20th, 2008, 07:52 PM
vpire vpire is offline
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Quote:
Originally Posted by buster.t
Hello,

I am not very experienced with SQL. I apologize if this is trivial. I have two tables:

Class
-----
ID (int)
Teacher (nvarchar)
Subject (nvarchar)

Student
--------
ID (int)
ClassID (int)
Name (nvarchar)

I am trying to write a SQL query that will give me the total number of students in each class. I have tried the following:

SELECT
c.ID,
c.Teacher,
c.Subject
COUNT(s.ID)
FROM
Class c LEFT OUTER JOINT ON Student s c.ID=s.ClassID

Unfortunately, that gives me an error of:
Column 'Class.Teacher' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

I'm afraid if I place everything in a GROUP BY clause, I will get some invalid results.

Can anyone please steer me in the correct direction?

Thank you!


You can give this a try
Code:
SELECT C.ID, C.TEACHER, C.SUBJECT, COUNT(S.ID)
FROM CLASS C, STUDENT S
WHERE C.ID = S.CLASSID
GROUP BY C.ID, C.SUBJECT, C.TEACHER
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  #4  
Old April 21st, 2008, 06:56 AM
pabloj's Avatar
pabloj pabloj is offline
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Quote:
Originally Posted by buster.t
...
I'm afraid if I place everything in a GROUP BY clause, I will get some invalid results.
...
Actually you could get invalid results by not putting everything in the group by.
Comments on this post
Annie79 agrees!
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  #5  
Old June 6th, 2008, 10:24 AM
sheetal999 sheetal999 is offline
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Try this
Try This
Select count(a.id),b.classid from class c,student b where c.id=b.id
and group by b.id,b.classid
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