Use of expressions or field aliases in GROUP BY clauses

Question

I've seen numerous references, even BNF syntax
diagrams, that suggest that Oracle's parser will accept an expression in a
GROUP BY clause; however, I've had no success whatsoever in getting this to
work. Here's an example of something I had hoped would work, but does not:
SELECT
account_id,
CASE
WHEN txn_date BETWEEN DATE '2006-06-01' AND DATE '2006-06-07' THEN 1
WHEN txn_date BETWEEN DATE '2006-06-08' AND DATE '2006-06-14' THEN 2
ELSE 3
END AS week_id,
COUNT(*) AS week_cnt
FROM myschema.my_random_table_name
GROUP BY account_id, week_id;
The interpreter gags on the use of "week_id" in the GROUP BY statement.
Evidently Oracle syntax doesn't support the use of positional designations
in aggregating statements either - I tried using the clause
GROUP BY 1, 2;
as the last line, and it didn't like this either.
Any assistance or suggestions you can offer would be greatly appreciated.
I prefer to let the DBMS engine do my aggregating for me as much as
possible, but without being able to aggregate relative to programmer-defined
fields, I am somewhat hamstrung.

Answer 1

try this :
SQL> select case when hire_date between '01-JAN-00' and '31-DEC-05' then 1 else 0 end col1, count(*)
2 from employees
3 group by col1;
group by col1
ERROR at line 3:
ORA-00904: "COL1": invalid identifier
SQL>
SQL>
SQL>
1 select case when hire_date between '01-JAN-00' and '31-DEC-05' then 1 else 0 end col1, count(*)
2 from employees
3* group by case when hire_date between '01-JAN-00' and '31-DEC-05' then 1 else 0 end
SQL> /
COL1 COUNT(*)
1 11
0 96