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Thread: conditional aggregates

conditional aggregates

From
Marcin Krawczyk
Date:
Hi list,

Can anyone advise me on creating an aggregate that would take additional parameter as a condition ? For example, say I have a table like this

id;value
1;45
2;13
3;0
4;90

I'd like to do something like this

SELECT min_some_cond_aggregate(value,0) FROM table

to get the minimal value from table greater than 0, in this case 13. 

I can't do SELECT min(value) FROM table WHERE value > 0 as this will mess my other computations. My current solution involves a function operating on the output of array_accum from the docs, but I'm looking for more elegant solution.

Is this possible at all ? I'm running 8.1.


regards
mk

Re: conditional aggregates

From
Pavel Stehule
Date:
Hello

use a CASE statement

http://www.postgresql.org/docs/7.4/static/functions-conditional.html

Regards

Pavel Stehule

2010/12/8 Marcin Krawczyk <jankes.mk@gmail.com>:
> Hi list,
> Can anyone advise me on creating an aggregate that would take additional
> parameter as a condition ? For example, say I have a table like this
> id;value
> 1;45
> 2;13
> 3;0
> 4;90
> I'd like to do something like this
> SELECT min_some_cond_aggregate(value,0) FROM table
> to get the minimal value from table greater than 0, in this case 13.
> I can't do SELECT min(value) FROM table WHERE value > 0 as this will mess my
> other computations. My current solution involves a function operating on the
> output of array_accum from the docs, but I'm looking for more elegant
> solution.
> Is this possible at all ? I'm running 8.1.
>
> regards
> mk
>

Re: conditional aggregates

From
Marcin Krawczyk
Date:
Yeah I know but I'm having problems creating sfunc fuction for the aggregate.


regards
mk


2010/12/8 Pavel Stehule <pavel.stehule@gmail.com>
Hello

use a CASE statement

http://www.postgresql.org/docs/7.4/static/functions-conditional.html

Regards

Pavel Stehule

2010/12/8 Marcin Krawczyk <jankes.mk@gmail.com>:
> Hi list,
> Can anyone advise me on creating an aggregate that would take additional
> parameter as a condition ? For example, say I have a table like this
> id;value
> 1;45
> 2;13
> 3;0
> 4;90
> I'd like to do something like this
> SELECT min_some_cond_aggregate(value,0) FROM table
> to get the minimal value from table greater than 0, in this case 13.
> I can't do SELECT min(value) FROM table WHERE value > 0 as this will mess my
> other computations. My current solution involves a function operating on the
> output of array_accum from the docs, but I'm looking for more elegant
> solution.
> Is this possible at all ? I'm running 8.1.
>
> regards
> mk
>

Re: conditional aggregates

From
"Marc Mamin"
Date:

something like ?

 

Select min (case when X > 0 then X end)

 

 

HTH,

 

Marc Mamin

 

From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Marcin Krawczyk
Sent: Mittwoch, 8. Dezember 2010 14:20
To: Pavel Stehule
Cc: pgsql-sql@postgresql.org
Subject: Re: [SQL] conditional aggregates

 

Yeah I know but I'm having problems creating sfunc fuction for the aggregate.

 


regards
mk

2010/12/8 Pavel Stehule <pavel.stehule@gmail.com>

Hello

use a CASE statement

http://www.postgresql.org/docs/7.4/static/functions-conditional.html

Regards

Pavel Stehule

2010/12/8 Marcin Krawczyk <jankes.mk@gmail.com>:

> Hi list,
> Can anyone advise me on creating an aggregate that would take additional
> parameter as a condition ? For example, say I have a table like this
> id;value
> 1;45
> 2;13
> 3;0
> 4;90
> I'd like to do something like this
> SELECT min_some_cond_aggregate(value,0) FROM table
> to get the minimal value from table greater than 0, in this case 13.
> I can't do SELECT min(value) FROM table WHERE value > 0 as this will mess my
> other computations. My current solution involves a function operating on the
> output of array_accum from the docs, but I'm looking for more elegant
> solution.
> Is this possible at all ? I'm running 8.1.
>
> regards
> mk
>

 

Re: conditional aggregates

From
Marcin Krawczyk
Date:
Thanks, it working.


pozdrowienia
mk


2010/12/8 Marc Mamin <M.Mamin@intershop.de>

something like ?

 

Select min (case when X > 0 then X end)

 

 

HTH,

 

Marc Mamin

 

From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Marcin Krawczyk
Sent: Mittwoch, 8. Dezember 2010 14:20
To: Pavel Stehule
Cc: pgsql-sql@postgresql.org
Subject: Re: [SQL] conditional aggregates

 

Yeah I know but I'm having problems creating sfunc fuction for the aggregate.

 


regards
mk

2010/12/8 Pavel Stehule <pavel.stehule@gmail.com>

Hello

use a CASE statement

http://www.postgresql.org/docs/7.4/static/functions-conditional.html

Regards

Pavel Stehule

2010/12/8 Marcin Krawczyk <jankes.mk@gmail.com>:

> Hi list,
> Can anyone advise me on creating an aggregate that would take additional
> parameter as a condition ? For example, say I have a table like this
> id;value
> 1;45
> 2;13
> 3;0
> 4;90
> I'd like to do something like this
> SELECT min_some_cond_aggregate(value,0) FROM table
> to get the minimal value from table greater than 0, in this case 13.
> I can't do SELECT min(value) FROM table WHERE value > 0 as this will mess my
> other computations. My current solution involves a function operating on the
> output of array_accum from the docs, but I'm looking for more elegant
> solution.
> Is this possible at all ? I'm running 8.1.
>
> regards
> mk
>