Creat view with a avg column - oracle

Question

I need to create a view VIEW UOS_VU_STUDENT_AVERAGE, one of the column requries average GRADE, SQL:
CREATE VIEW UOS_VU_STUDENT_AVERAGE AS
SELECT STUDENT.FIRST_NAME, STUDENT.LAST_NAME, STUDENT_MODULE.GRADE
FROM STUDENT, STUDENT_MODULE
WHERE STUDENT_ID<120000001
How could I avg grade in this sql?

Answer 1

try
CREATE VIEW UOS_VU_STUDENT_AVERAGE AS
SELECT STUDENT.FIRST_NAME, STUDENT.LAST_NAME, avg(STUDENT_MODULE.GRADE)
FROM STUDENT, STUDENT_MODULE
WHERE STUDENT_ID<120000001
group by STUDENT.FIRST_NAME, STUDENT.LAST_NAME
as zerkms commented, there is no join condition, you probably need something like this:
CREATE VIEW UOS_VU_STUDENT_AVERAGE AS
SELECT STUDENT.FIRST_NAME, STUDENT.LAST_NAME, avg(STUDENT_MODULE.GRADE)
FROM STUDENT join STUDENT_MODULE on student_module.STUDENT_ID = student.id
WHERE STUDENT_ID<120000001
group by STUDENT.FIRST_NAME, STUDENT.LAST_NAME
(I'm just guessing that the FK is on student_module.STUDENT_ID = student.id)

Answer 2

You have to use "Group by" for any mathematical function like
AVG ( [ ALL | DISTINCT ] expression )
for example ..
SELECT id, AVG(salary) from tablename GROUP BY filedname

Answer 3

You'll need to do something like the following. I've made a few assumptions on the structure of the tables.
CREATE VIEW uos_vu_student_average AS
SELECT first_name, last_name, AVG(grade) avg_grade
FROM student, student_module
WHERE student.student_id = student_module.student_id
AND student.student_id < 120000001
GROUP BY first_name, last_name;
In your example, and as was pointed out by a previous poster, you don't have a join in your original example so it would just average all the grades together, regardless of the student_id. The result would show everyone with the same average grade.
When doing aggregate functions inside a view you also need to assign the resulting column an alias, so you can reference it in some manner when performing DML against the view. In this case I assigned it avg_grade.