Using column aliases in having clause error

Question

This is the query I'm trying to run.
select concat(concat(student.last_name, ', '), student.first_name) student, count(school_apply.decision) decision
from student, school_apply
where student.student_id = school_apply.student_id
and school_apply.decision = 'accepted'
having decision < 3
group by student.last_name, student.first_name
order by count(school_apply.decision) desc, student.last_name, student.first_name;
I got the following error
Error at Command Line:5 Column:7
Error report:
SQL Error: ORA-00979: not a GROUP BY expression
00979. 00000 - "not a GROUP BY expression"
if in the having I use count(school_apply.decision) instead of the alias, it works fine. Why is this? and how can I use the alias'd column in the SQL?

Answer 1

Hi,
user4038196 wrote:
This is the query I'm trying to run.
select concat(concat(student.last_name, ', '), student.first_name) student, count(school_apply.decision) decision
from student, school_apply
where student.student_id = school_apply.student_id
and school_apply.decision = 'accepted'
having decision < 3
group by student.last_name, student.first_name
order by count(school_apply.decision) desc, student.last_name, student.first_name;
I got the following error
Error at Command Line:5 Column:7
Error report:
SQL Error: ORA-00979: not a GROUP BY expression
00979. 00000 - "not a GROUP BY expression"
if in the having I use count(school_apply.decision) instead of the alias, it works fine. Why is this? and how can I use the alias'd column in the SQL?When you define a column alias, like decision, in a query, you can use it in the ORDER BY clause. That's the only place in that query where you can use it.
You can always assign the alias in a sub-query, then use it anywhere you want to in a super-query, like this:
WITH     got_aggregates     AS
     select   student.last_name || ', '
                              || student.first_name     AS student
     ,        count (school_apply.decision)           AS decision
     from       student
     ,       school_apply
     where        student.student_id     = school_apply.student_id
     and       school_apply.decision = 'accepted'
     group by  student.last_name
     ,            student.first_name
SELECT    *
FROM       got_aggregates
WHERE       decision     < 3          -- Okay to use alias from sub-query
ORDER BY  decision     DESC          -- Okay to use alias from sub-query
,            student               -- Okay to use alias from sub-query
;