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Posted to derby-user@db.apache.org by Robert Enyedi <ro...@intland.com> on 2006/08/28 17:58:15 UTC
How to emulate multiple DISTINCT aggregates?
Hi,
When trying to use multiple DISTINCT aggregates in Derby:
/SELECT COUNT(distinct editable), COUNT( distinct visible )
FROM item/
the following error is reported:
/ERROR 42Z02: Multiple DISTINCT aggregates are not supported at this time./
For a simple query one could write:
/SELECT COUNT(distinct editable) AS editable_count, COUNT( (SELECT
DISTINCT visible FROM item) )
FROM item/
but this is actually pretty uncomfortable and unmaintainable in a larger
query.
Does anyone know an elegant overcome for this Derby limitation?
Thanks,
Robert
Re: How to emulate multiple DISTINCT aggregates?
Posted by Robert Enyedi <ro...@intland.com>.
Thanks, Ali. But this is actually a variant of the solution that I
proposed. The main problem that I see with it is that you need to
duplicate the WHERE field of the main query in all the subqueries and
this is just an overkill.
Regards,
Robert
Suavi Ali Demir wrote:
> That query needs to be modified little bit. It does not work when
> my table contains:
>
> 1 1 1
> 2 2 2
> 1 1 3
>
>
> result is 3,3,3, where as it should have been 2,2,3.
>
> This one works:
>
> SELECT
> (SELECT COUNT(DISTINCT b.field1) FROM table_a b) as field1_count,
> (SELECT COUNT(DISTINCT c.field2) FROM table_a c) as field2_count,
> (SELECT COUNT(DISTINCT d.field3) FROM table_a d) as field3_count
> FROM SYSIBM.SYSDUMMY1
>
> Regards,
> Ali
>
> */derby@segel.com/* wrote:
>
>
> Hi,
>
> Uhm you can't do what you want to do as written....
>
> When you say SELECT COUNT(DISTINCT blah), it has to be unique to
> your query.
> So no multiple COUNT(DISTINCTS xxx) allowed in a single query.
> However here's a work around that may help...
>
> SELECT COUNT(a.field1), COUNT(a.field2), COUNT(a.field3) ...
> FROM table_a a
> WHERE a.field1 in ( SELECT DISTINCT b.field1 FROM table_a b)
> AND a.field2 in ( SELECT DISTINCT b.field2 FROM table_a b)
> AND a.field3 in ( SELECT DISTINCT b.field3 FROM table_a b)
> ...
>
> Well you get the idea.
>
> It's then pretty straight forward.
> Each subselect returns the distinct set of elements and then your
> outer
> select returns the count on these unique subsets.
>
> I just tried it in Informix (I happen to have a table with a couple of
> string columns of data that I am working on.)
> Should work in Derby. Its all standard SQL
>
> But Hey! What do I know?
>
> -G
>
> > -----Original Message-----
> > From: Robert Enyedi [mailto:robert.enyedi@intland.com]
> > Sent: Monday, August 28, 2006 10:58 AM
> > To: Derby Discussion
> > Subject: How to emulate multiple DISTINCT aggregates?
> >
> > Hi,
> >
> > When trying to use multiple DISTINCT aggregates in Derby:
> >
> > /SELECT COUNT(distinct editable), COUNT( distinct visible )
> > FROM item/
> >
> > the following error is reported:
> >
> > /ERROR 42Z02: Multiple DISTINCT aggregates are not supported at this
> > time./
> >
> > For a simple query one could write:
> >
> > /SELECT COUNT(distinct editable) AS editable_count, COUNT( (SELECT
> > DISTINCT visible FROM item) )
> > FROM item/
> >
> > but this is actually pretty uncomfortable and unmaintainable in
> a larger
> > query.
> >
> > Does anyone know an elegant overcome for this Derby limitation?
> >
> > Thanks,
> > Robert
>
>
>
RE: How to emulate multiple DISTINCT aggregates?
Posted by Michael Segel <ms...@segel.com>.
Ok,
Yeah, you're right.
I'm trying to think about what I did in my query that gave me the right
result.
In my test table, there were 65K rows and I was able to get the correct
count.
So I guess I'll have to go back to see what I did.
> -----Original Message-----
> From: Robert Enyedi [mailto:robert.enyedi@intland.com]
> Sent: Tuesday, August 29, 2006 2:43 AM
> To: Derby Discussion
> Subject: Re: How to emulate multiple DISTINCT aggregates?
>
> I can confirm what Ali said because {3,3,3} is the result I also receive
> on Derby.
>
> However, it seems the correct result to me. Just think about it:
>
> SELECT COUNT(tmp1.f1)
> FROM tmp1
> WHERE tmp1.f1 in ( SELECT DISTINCT b.f1 FROM tmp1 b)
>
> This basically counts the number of values field f1 has.
>
> Regards,
> Robert
>
> derby@segel.com wrote:
> >
> > That doesn't make sense.
> >
> > Each sub select statement should have returned the following
> >
> > Field A {1,2}
> >
> > Field B {1,2}
> >
> > Field C {1,2,3}
> >
> > Then in the original select, your counts should be {2,2,3};
> >
> > Note: I used Informix.
> >
> > There is something interesting going on. You're using a dummy table as
> > a wrapper for 3.
> >
> > Now I wonder what the optimizer thinks of this and how, if at all,
> > does it parallelize the query?
> >
> > I'll try my sql method on a similar table to yours, but I do think the
> > response you saw wasn't correct.
> >
> > ------------------------------------------------------------------------
> >
> > *From:* Suavi Ali Demir [mailto:demir4@yahoo.com]
> > *Sent:* Monday, August 28, 2006 3:52 PM
> > *To:* Derby Discussion; msegel@segel.com
> > *Subject:* RE: How to emulate multiple DISTINCT aggregates?
> >
> > That query needs to be modified little bit. It does not work when
> >
> > my table contains:
> >
> > 1
> >
> >
> >
> > 1
> >
> >
> >
> > 1
> >
> > 2
> >
> >
> >
> > 2
> >
> >
> >
> > 2
> >
> > 1
> >
> >
> >
> > 1
> >
> >
> >
> > 3
> >
> > result is 3,3,3, where as it should have been 2,2,3.
> >
> > This one works:
> >
> > SELECT
> > (SELECT COUNT(DISTINCT b.field1) FROM table_a b) as field1_count,
> > (SELECT COUNT(DISTINCT c.field2) FROM table_a c) as field2_count,
> > (SELECT COUNT(DISTINCT d.field3) FROM table_a d) as field3_count
> > FROM SYSIBM.SYSDUMMY1
> >
> > Regards,
> >
> > Ali
> >
> >
> > */derby@segel.com/* wrote:
> >
> >
> > Hi,
> >
> > Uhm you can't do what you want to do as written....
> >
> > When you say SELECT COUNT(DISTINCT blah), it has to be unique to
> > your query.
> > So no multiple COUNT(DISTINCTS xxx) allowed in a single query.
> > However here's a work around that may help...
> >
> > SELECT COUNT(a.field1), COUNT(a.field2), COUNT(a.field3) ...
> > FROM table_a a
> > WHERE a.field1 in ( SELECT DISTINCT b.field1 FROM table_a b)
> > AND a.field2 in ( SELECT DISTINCT b.field2 FROM table_a b)
> > AND a.field3 in ( SELECT DISTINCT b.field3 FROM table_a b)
> > ...
> >
> > Well you get the idea.
> >
> > It's then pretty straight forward.
> > Each subselect returns the distinct set of elements and then your
> > outer
> > select returns the count on these unique subsets.
> >
> > I just tried it in Informix (I happen to have a table with a couple
> of
> > string columns of data that I am working on.)
> > Should work in Derby. Its all standard SQL
> >
> > But Hey! What do I know?
> >
> > -G
> >
> > > -----Original Message-----
> > > From: Robert Enyedi [mailto:robert.enyedi@intland.com]
> > > Sent: Monday, August 28, 2006 10:58 AM
> > > To: Derby Discussion
> > > Subject: How to emulate multiple DISTINCT aggregates?
> > >
> > > Hi,
> > >
> > > When trying to use multiple DISTINCT aggregates in Derby:
> > >
> > > /SELECT COUNT(distinct editable), COUNT( distinct visible )
> > > FROM item/
> > >
> > > the following error is reported:
> > >
> > > /ERROR 42Z02: Multiple DISTINCT aggregates are not supported at
> this
> > > time./
> > >
> > > For a simple query one could write:
> > >
> > > /SELECT COUNT(distinct editable) AS editable_count, COUNT( (SELECT
> > > DISTINCT visible FROM item) )
> > > FROM item/
> > >
> > > but this is actually pretty uncomfortable and unmaintainable in a
> > larger
> > > query.
> > >
> > > Does anyone know an elegant overcome for this Derby limitation?
> > >
> > > Thanks,
> > > Robert
> >
Re: How to emulate multiple DISTINCT aggregates?
Posted by Robert Enyedi <ro...@intland.com>.
I can confirm what Ali said because {3,3,3} is the result I also receive
on Derby.
However, it seems the correct result to me. Just think about it:
SELECT COUNT(tmp1.f1)
FROM tmp1
WHERE tmp1.f1 in ( SELECT DISTINCT b.f1 FROM tmp1 b)
This basically counts the number of values field f1 has.
Regards,
Robert
derby@segel.com wrote:
>
> That doesn’t make sense.
>
> Each sub select statement should have returned the following
>
> Field A {1,2}
>
> Field B {1,2}
>
> Field C {1,2,3}
>
> Then in the original select, your counts should be {2,2,3};
>
> Note: I used Informix.
>
> There is something interesting going on. You’re using a dummy table as
> a wrapper for 3.
>
> Now I wonder what the optimizer thinks of this and how, if at all,
> does it parallelize the query?
>
> I’ll try my sql method on a similar table to yours, but I do think the
> response you saw wasn’t correct.
>
> ------------------------------------------------------------------------
>
> *From:* Suavi Ali Demir [mailto:demir4@yahoo.com]
> *Sent:* Monday, August 28, 2006 3:52 PM
> *To:* Derby Discussion; msegel@segel.com
> *Subject:* RE: How to emulate multiple DISTINCT aggregates?
>
> That query needs to be modified little bit. It does not work when
>
> my table contains:
>
> 1
>
>
>
> 1
>
>
>
> 1
>
> 2
>
>
>
> 2
>
>
>
> 2
>
> 1
>
>
>
> 1
>
>
>
> 3
>
> result is 3,3,3, where as it should have been 2,2,3.
>
> This one works:
>
> SELECT
> (SELECT COUNT(DISTINCT b.field1) FROM table_a b) as field1_count,
> (SELECT COUNT(DISTINCT c.field2) FROM table_a c) as field2_count,
> (SELECT COUNT(DISTINCT d.field3) FROM table_a d) as field3_count
> FROM SYSIBM.SYSDUMMY1
>
> Regards,
>
> Ali
>
>
> */derby@segel.com/* wrote:
>
>
> Hi,
>
> Uhm you can't do what you want to do as written....
>
> When you say SELECT COUNT(DISTINCT blah), it has to be unique to
> your query.
> So no multiple COUNT(DISTINCTS xxx) allowed in a single query.
> However here's a work around that may help...
>
> SELECT COUNT(a.field1), COUNT(a.field2), COUNT(a.field3) ...
> FROM table_a a
> WHERE a.field1 in ( SELECT DISTINCT b.field1 FROM table_a b)
> AND a.field2 in ( SELECT DISTINCT b.field2 FROM table_a b)
> AND a.field3 in ( SELECT DISTINCT b.field3 FROM table_a b)
> ...
>
> Well you get the idea.
>
> It's then pretty straight forward.
> Each subselect returns the distinct set of elements and then your
> outer
> select returns the count on these unique subsets.
>
> I just tried it in Informix (I happen to have a table with a couple of
> string columns of data that I am working on.)
> Should work in Derby. Its all standard SQL
>
> But Hey! What do I know?
>
> -G
>
> > -----Original Message-----
> > From: Robert Enyedi [mailto:robert.enyedi@intland.com]
> > Sent: Monday, August 28, 2006 10:58 AM
> > To: Derby Discussion
> > Subject: How to emulate multiple DISTINCT aggregates?
> >
> > Hi,
> >
> > When trying to use multiple DISTINCT aggregates in Derby:
> >
> > /SELECT COUNT(distinct editable), COUNT( distinct visible )
> > FROM item/
> >
> > the following error is reported:
> >
> > /ERROR 42Z02: Multiple DISTINCT aggregates are not supported at this
> > time./
> >
> > For a simple query one could write:
> >
> > /SELECT COUNT(distinct editable) AS editable_count, COUNT( (SELECT
> > DISTINCT visible FROM item) )
> > FROM item/
> >
> > but this is actually pretty uncomfortable and unmaintainable in a
> larger
> > query.
> >
> > Does anyone know an elegant overcome for this Derby limitation?
> >
> > Thanks,
> > Robert
>
RE: How to emulate multiple DISTINCT aggregates?
Posted by Suavi Ali Demir <de...@yahoo.com>.
Let's look at the query differently to see what it is trying to say:
SELECT count(some columns) FROM table_a a
WHERE ( some field1 criteria thats always true )
AND ( some field2 criteria thats always true )
AND (some field3 criteria thats always true )
The where clause will always be true. For a given row, if where clause is true, the tuples of that row will be returned. That would make 3 rows (all rows) returned in this case since where clause is always true. And which column we count does not matter i guess.
Regards,
Ali
derby@segel.com wrote:
v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} st1\:*{behavior:url(#default#ieooui) } That doesnt make sense.
Each sub select statement should have returned the following
Field A {1,2}
Field B {1,2}
Field C {1,2,3}
Then in the original select, your counts should be {2,2,3};
Note: I used Informix.
There is something interesting going on. Youre using a dummy table as a wrapper for 3.
Now I wonder what the optimizer thinks of this and how, if at all, does it parallelize the query?
Ill try my sql method on a similar table to yours, but I do think the response you saw wasnt correct.
---------------------------------
From: Suavi Ali Demir [mailto:demir4@yahoo.com]
Sent: Monday, August 28, 2006 3:52 PM
To: Derby Discussion; msegel@segel.com
Subject: RE: How to emulate multiple DISTINCT aggregates?
That query needs to be modified little bit. It does not work when
my table contains:
1
1
1
2
2
2
1
1
3
result is 3,3,3, where as it should have been 2,2,3.
This one works:
SELECT
(SELECT COUNT(DISTINCT b.field1) FROM table_a b) as field1_count,
(SELECT COUNT(DISTINCT c.field2) FROM table_a c) as field2_count,
(SELECT COUNT(DISTINCT d.field3) FROM table_a d) as field3_count
FROM SYSIBM.SYSDUMMY1
Regards,
Ali
derby@segel.com wrote:
Hi,
Uhm you can't do what you want to do as written....
When you say SELECT COUNT(DISTINCT blah), it has to be unique to your query.
So no multiple COUNT(DISTINCTS xxx) allowed in a single query.
However here's a work around that may help...
SELECT COUNT(a.field1), COUNT(a.field2), COUNT(a.field3) ...
FROM table_a a
WHERE a.field1 in ( SELECT DISTINCT b.field1 FROM table_a b)
AND a.field2 in ( SELECT DISTINCT b.field2 FROM table_a b)
AND a.field3 in ( SELECT DISTINCT b.field3 FROM table_a b)
...
Well you get the idea.
It's then pretty straight forward.
Each subselect returns the distinct set of elements and then your outer
select returns the count on these unique subsets.
I just tried it in Informix (I happen to have a table with a couple of
string columns of data that I am working on.)
Should work in Derby. Its all standard SQL
But Hey! What do I know?
-G
> -----Original Message-----
> From: Robert Enyedi [mailto:robert.enyedi@intland.com]
> Sent: Monday, August 28, 2006 10:58 AM
> To: Derby Discussion
> Subject: How to emulate multiple DISTINCT aggregates?
>
> Hi,
>
> When trying to use multiple DISTINCT aggregates in Derby:
>
> /SELECT COUNT(distinct editable), COUNT( distinct visible )
> FROM item/
>
> the following error is reported:
>
> /ERROR 42Z02: Multiple DISTINCT aggregates are not supported at this
> time./
>
> For a simple query one could write:
>
> /SELECT COUNT(distinct editable) AS editable_count, COUNT( (SELECT
> DISTINCT visible FROM item) )
> FROM item/
>
> but this is actually pretty uncomfortable and unmaintainable in a larger
> query.
>
> Does anyone know an elegant overcome for this Derby limitation?
>
> Thanks,
> Robert
RE: How to emulate multiple DISTINCT aggregates?
Posted by de...@segel.com.
That doesn't make sense.
Each sub select statement should have returned the following
Field A {1,2}
Field B {1,2}
Field C {1,2,3}
Then in the original select, your counts should be {2,2,3};
Note: I used Informix.
There is something interesting going on. You're using a dummy table as a
wrapper for 3.
Now I wonder what the optimizer thinks of this and how, if at all, does it
parallelize the query?
I'll try my sql method on a similar table to yours, but I do think the
response you saw wasn't correct.
_____
From: Suavi Ali Demir [mailto:demir4@yahoo.com]
Sent: Monday, August 28, 2006 3:52 PM
To: Derby Discussion; msegel@segel.com
Subject: RE: How to emulate multiple DISTINCT aggregates?
That query needs to be modified little bit. It does not work when
my table contains:
1
1
1
2
2
2
1
1
3
result is 3,3,3, where as it should have been 2,2,3.
This one works:
SELECT
(SELECT COUNT(DISTINCT b.field1) FROM table_a b) as field1_count,
(SELECT COUNT(DISTINCT c.field2) FROM table_a c) as field2_count,
(SELECT COUNT(DISTINCT d.field3) FROM table_a d) as field3_count
FROM SYSIBM.SYSDUMMY1
Regards,
Ali
derby@segel.com wrote:
Hi,
Uhm you can't do what you want to do as written....
When you say SELECT COUNT(DISTINCT blah), it has to be unique to your query.
So no multiple COUNT(DISTINCTS xxx) allowed in a single query.
However here's a work around that may help...
SELECT COUNT(a.field1), COUNT(a.field2), COUNT(a.field3) ...
FROM table_a a
WHERE a.field1 in ( SELECT DISTINCT b.field1 FROM table_a b)
AND a.field2 in ( SELECT DISTINCT b.field2 FROM table_a b)
AND a.field3 in ( SELECT DISTINCT b.field3 FROM table_a b)
...
Well you get the idea.
It's then pretty straight forward.
Each subselect returns the distinct set of elements and then your outer
select returns the count on these unique subsets.
I just tried it in Informix (I happen to have a table with a couple of
string columns of data that I am working on.)
Should work in Derby. Its all standard SQL
But Hey! What do I know?
-G
> -----Original Message-----
> From: Robert Enyedi [mailto:robert.enyedi@intland.com]
> Sent: Monday, August 28, 2006 10:58 AM
> To: Derby Discussion
> Subject: How to emulate multiple DISTINCT aggregates?
>
> Hi,
>
> When trying to use multiple DISTINCT aggregates in Derby:
>
> /SELECT COUNT(distinct editable), COUNT( distinct visible )
> FROM item/
>
> the following error is reported:
>
> /ERROR 42Z02: Multiple DISTINCT aggregates are not supported at this
> time./
>
> For a simple query one could write:
>
> /SELECT COUNT(distinct editable) AS editable_count, COUNT( (SELECT
> DISTINCT visible FROM item) )
> FROM item/
>
> but this is actually pretty uncomfortable and unmaintainable in a larger
> query.
>
> Does anyone know an elegant overcome for this Derby limitation?
>
> Thanks,
> Robert
RE: How to emulate multiple DISTINCT aggregates?
Posted by Suavi Ali Demir <de...@yahoo.com>.
That query needs to be modified little bit. It does not work when
my table contains:
1 1 1 2 2 2 1 1 3
result is 3,3,3, where as it should have been 2,2,3.
This one works:
SELECT
(SELECT COUNT(DISTINCT b.field1) FROM table_a b) as field1_count,
(SELECT COUNT(DISTINCT c.field2) FROM table_a c) as field2_count,
(SELECT COUNT(DISTINCT d.field3) FROM table_a d) as field3_count
FROM SYSIBM.SYSDUMMY1
Regards,
Ali
derby@segel.com wrote:
Hi,
Uhm you can't do what you want to do as written....
When you say SELECT COUNT(DISTINCT blah), it has to be unique to your query.
So no multiple COUNT(DISTINCTS xxx) allowed in a single query.
However here's a work around that may help...
SELECT COUNT(a.field1), COUNT(a.field2), COUNT(a.field3) ...
FROM table_a a
WHERE a.field1 in ( SELECT DISTINCT b.field1 FROM table_a b)
AND a.field2 in ( SELECT DISTINCT b.field2 FROM table_a b)
AND a.field3 in ( SELECT DISTINCT b.field3 FROM table_a b)
...
Well you get the idea.
It's then pretty straight forward.
Each subselect returns the distinct set of elements and then your outer
select returns the count on these unique subsets.
I just tried it in Informix (I happen to have a table with a couple of
string columns of data that I am working on.)
Should work in Derby. Its all standard SQL
But Hey! What do I know?
-G
> -----Original Message-----
> From: Robert Enyedi [mailto:robert.enyedi@intland.com]
> Sent: Monday, August 28, 2006 10:58 AM
> To: Derby Discussion
> Subject: How to emulate multiple DISTINCT aggregates?
>
> Hi,
>
> When trying to use multiple DISTINCT aggregates in Derby:
>
> /SELECT COUNT(distinct editable), COUNT( distinct visible )
> FROM item/
>
> the following error is reported:
>
> /ERROR 42Z02: Multiple DISTINCT aggregates are not supported at this
> time./
>
> For a simple query one could write:
>
> /SELECT COUNT(distinct editable) AS editable_count, COUNT( (SELECT
> DISTINCT visible FROM item) )
> FROM item/
>
> but this is actually pretty uncomfortable and unmaintainable in a larger
> query.
>
> Does anyone know an elegant overcome for this Derby limitation?
>
> Thanks,
> Robert
RE: How to emulate multiple DISTINCT aggregates?
Posted by de...@segel.com.
Hi,
Uhm you can't do what you want to do as written....
When you say SELECT COUNT(DISTINCT blah), it has to be unique to your query.
So no multiple COUNT(DISTINCTS xxx) allowed in a single query.
However here's a work around that may help...
SELECT COUNT(a.field1), COUNT(a.field2), COUNT(a.field3) ...
FROM table_a a
WHERE a.field1 in ( SELECT DISTINCT b.field1 FROM table_a b)
AND a.field2 in ( SELECT DISTINCT b.field2 FROM table_a b)
AND a.field3 in ( SELECT DISTINCT b.field3 FROM table_a b)
...
Well you get the idea.
It's then pretty straight forward.
Each subselect returns the distinct set of elements and then your outer
select returns the count on these unique subsets.
I just tried it in Informix (I happen to have a table with a couple of
string columns of data that I am working on.)
Should work in Derby. Its all standard SQL
But Hey! What do I know?
-G
> -----Original Message-----
> From: Robert Enyedi [mailto:robert.enyedi@intland.com]
> Sent: Monday, August 28, 2006 10:58 AM
> To: Derby Discussion
> Subject: How to emulate multiple DISTINCT aggregates?
>
> Hi,
>
> When trying to use multiple DISTINCT aggregates in Derby:
>
> /SELECT COUNT(distinct editable), COUNT( distinct visible )
> FROM item/
>
> the following error is reported:
>
> /ERROR 42Z02: Multiple DISTINCT aggregates are not supported at this
> time./
>
> For a simple query one could write:
>
> /SELECT COUNT(distinct editable) AS editable_count, COUNT( (SELECT
> DISTINCT visible FROM item) )
> FROM item/
>
> but this is actually pretty uncomfortable and unmaintainable in a larger
> query.
>
> Does anyone know an elegant overcome for this Derby limitation?
>
> Thanks,
> Robert