From: George Francis <gfrancis1@gmail.com>
To: Jasmin Dizdarevic <jasmin.dizdarevic@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: joining one record according to max value
Date: Wed, 12 Jan 2011 17:53:56 -0500
Message-ID: <AANLkTikGmQphfEXcGxGx7LbbrwJGTW=Oi941O2sm=Fty@mail.gmail.com> (raw)
In-Reply-To: <AANLkTi=sRZFOFBEo2bf75iNd0JDkv9md03hAzB95oUMo@mail.gmail.com>
References: <AANLkTik6-BWRrRjmSCym3y4tmYkg+QsuqS-dxBti9Cqr@mail.gmail.com>
<AANLkTi=vELQyTFEB29Epkm_ZCPGLdQY+DT+cOZ3mL6VT@mail.gmail.com>
<AANLkTikb8OHdGEM74yMk=fuxGucm+4heY62N6CQa-hEm@mail.gmail.com>
<AANLkTi=sRZFOFBEo2bf75iNd0JDkv9md03hAzB95oUMo@mail.gmail.com>
Close! but I need the name of the LEVEL with highest score, and I dont
think I can get it this way.
Thanks for trying though!
On Wed, Jan 12, 2011 at 5:49 PM, Jasmin Dizdarevic <
jasmin.dizdarevic@gmail.com> wrote:
> It's currently late, so excuse me if I'm wrong. Is this, what you like to
> have?
>
> select sl.source_id, max(score) from source s
> inner join sourcelevel sl on s.source_id = sl.source_id
> inner join level l on sl.level_id = l.level_id
> group by 1
>
> This is the highest score per source_id.
>
> 2011/1/12 George Francis <gfrancis1@gmail.com>
>
>> hmm, but if I try to constrain the inner query to the source_id of the
>> outer query I get an error as follows:
>>
>> select source.source_id, score, name from source
>> left join ( select * from sourcelevel, level where sourcelevel.level_id =
>> level.level_id and sourcelevel.source_id = source.source_id order by score
>> desc limit 1 )
>> as temp on temp.source_id = source.source_id;
>>
>> ERROR: invalid reference to FROM-clause entry for table "source"
>>
>> LINE 14: ...l_id = level.level_id and sourcelevel.source_id =
>> source.sou...
>>
>> ^
>>
>> HINT: There is an entry for table "source", but it cannot be referenced
>> from this part of the query.
>>
>>
>>
>> ********** Error **********
>>
>>
>> ERROR: invalid reference to FROM-clause entry for table "source"
>>
>> SQL state: 42P01
>>
>> Hint: There is an entry for table "source", but it cannot be referenced
>> from this part of the query.
>>
>> Character: 601
>>
>>
>> On Wed, Jan 12, 2011 at 5:35 PM, Jasmin Dizdarevic <
>> jasmin.dizdarevic@gmail.com> wrote:
>>
>>> Because of the "score desc limit 1". The subselect returns only the
>>> higest score and this is level 2.
>>>
>>> 2011/1/12 George Francis <gfrancis1@gmail.com>
>>>
>>> The following sql is intended to produce a list of all unique SOURCEs,
>>>> along with the corresponding LEVEL.NAME for LEVEL with highest SCORE
>>>> value via SOURCELEVEL.
>>>>
>>>> I'd like to know why it doesn't return a SCORE value for SOURCE with id
>>>> 3, despite there being a SOURCELEVEL entry for it.
>>>>
>>>> Many thanks,
>>>>
>>>>
>>>> drop table if exists source;
>>>>
>>>> drop table if exists sourcelevel;
>>>>
>>>> drop table if exists level;
>>>>
>>>>
>>>> create table source ( source_id int );
>>>>
>>>> create table sourcelevel ( source_id int, level_id int);
>>>>
>>>> create table level ( level_id int, score int, name text );
>>>>
>>>>
>>>> insert into source values (1), (2), (3);
>>>>
>>>> insert into level values ( 1, 10 ,'alpha' ), ( 2, 20, 'beta' ), ( 3, 15,
>>>> 'kappa' );
>>>>
>>>> insert into sourcelevel values ( 1, 1 ), ( 1,2 ), ( 3,3 );
>>>>
>>>>
>>>> select source.source_id, score, name from source
>>>>
>>>> left join ( select * from sourcelevel, level where sourcelevel.level_id
>>>> = level.level_id order by score desc limit 1 )
>>>>
>>>> as temp on temp.source_id = source.source_id;
>>>>
>>>> --
>>>> George
>>>>
>>>
>>>
>>
>>
>> --
>> George Francis
>> e-mail: gfrancis1@gmail.com
>>
>
>
--
George Francis
e-mail: gfrancis1@gmail.com
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Cc: gfrancis1@gmail.com, jasmin.dizdarevic@gmail.com
Subject: Re: joining one record according to max value
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