Thanks all,
My question was related more to the 'design' of SQL language. To my mind the
expression COUNT(DISTINCT a,b) looked a natural extension of the syntax
COUNT(DISTINCT a). Even COUNT(DISTINCT(a,b)) would look good enough to me.
Probably it's too trivial a thing to bother about. Using the subquery would
very well give the desired results.
I have been thinking of reading CJ Date and other experts' articles on the
design (and limitations) of SQL, but couldn't find any good resources on the
net. If you know of any links, then can you please let me know?
Thanks once again,
Charu.
-----Original Message-----
Sent: Wednesday, January 29, 2003 10:04 PM
To: Multiple recipients of list ORACLE-L
Charu,
The COUNT() function requires a single expression. "ename, job" is
not a valid expression. "ename||job" is a valid expression since it will
return a single value.
Another alternative would be
select count(*)
from (select distinct ename, job from emp);
Dan Fink
-----Original Message-----
Sent: Wednesday, January 29, 2003 11:19 AM
To: Multiple recipients of list ORACLE-L
Hello Listers,
How to find out the COUNT of DISTINCT values of multiple columns?
For eg.
SQL> SELECT DISTINCT ename FROM emp;
-- This works.
SQL> SELECT COUNT(DISTINCT ename) FROM emp;
-- So does this.
SQL> SELECT DISTINCT ename, job FROM emp;
-- And this too.
SQL> SELECT COUNT(DISTINCT ename, job) FROM emp;
-- So why does this fail?
I can do a COUNT(DISTINCT ename || job), but that doesn't seem to be elegant
way of doing it.
I have a feeling I might be missing some fairly basic syntax, but feeling
dumb is better than suspense.
Thanks & regards,
Charu.
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