RE: SQL question

Joshi,

SELECT count(*)
FROM (SELECT count(*)

      FROM flight_legs 
      GROUP BY d_actual_time, event_type);

SELECT count(*)
FROM (SELECT DISTINCT d_actual_time, event_type

          FROM flight_legs );

The first one took about 37 seconds in returning a count of 357331. The second statement was about 10 seconds quicker.

Jerry Whittle
ASIFICS DBA
NCI Information Systems Inc.
jerome.whittle_at_scott.af.mil
618-622-4145

> -----Original Message-----
> From: Charu Joshi [SMTP:joshic_at_mahindrabt.com]
>
> 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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