Re: Bucketing Row Data in columns - Mailing list pgsql-sql

I admit that must be a more elegant and faster solution with pl/psql (or 
whatever other languages)

As I don't know nothing about pl/psql I tried with pure sql (if you don't 
have a hunting dog, hunt with a cat)

But obviously this solution doesn't scale well if you have a giant table 
with lots of columns

----- Original Message ----- 
From: "Rob Sargent" <robjsargent@gmail.com>
To: <pgsql-sql@postgresql.org>
Sent: Thursday, June 25, 2009 4:57 PM
Subject: Re: [SQL] Bucketing Row Data in columns


>I would be suspicious of this sort of solution of turning rows into columns 
>by mean of a series of correlated sub-selects.  Once the data set gets 
>large and the number of columns goes over 2 or 3 this will in all 
>likelihood not perform well. I had the pleasure of re-writing a "report" 
>which was based on count() (similar to sum()) per user_id with the counts 
>going into various columns per user.  18000 users, a dozen columns from 
>table of 2 million rows, report took >1,000,000 seconds (yes almost 12 
>days) to complete.  Re-write runs in 5-10 minutes (now at 10M rows) by 
>getting the counts as rows (user, item, count) into a temp table and making 
>the columns from the temp table (pl/psql)  Getting the counts takes half 
>the time, making the flattened report takes half the time.
>
>
>
>
> Oliveiros Cristina wrote:
>> Hello, Sandeep,
>>  I am not sure if this is what you want.
>>  I came up with this query
>>  SELECT *
>> FROM (SELECT user_id,SUM(amount) as day1 FROM t1 WHERE create_timestamp = 
>> '2009-1-1' GROUP BY "user_id") a
>> NATURAL FULL JOIN (SELECT user_id,SUM(amount) as day2 FROM t1 WHERE 
>> create_timestamp = '2009-1-2' GROUP BY "user_id") b
>> NATURAL FULL JOIN (SELECT user_id,SUM(amount) as day3 FROM t1 WHERE 
>> create_timestamp = '2009-1-3' GROUP BY "user_id") c
>>  The solution is not totally correct because it returns NULL in the 
>> places you return 0.
>> It seems the SUM() returns NULL when it gets an all NULL column...
>> Is it problematic for your application ?
>>  Also, i 'm not sure if I fully understand your last sentence
>> /lets assume the buckets are fixed i.e 3 only. but I wish to get them 
>> unlimited i.e day 1 to day 20./
>>  You say that the buckets are fixed at 3. So, you mean the table output 
>> will always have 4 columns? 3 days plus one for user_id ?
>> If you want 20 buckets it must be a different query...
>>  Could you please clarify what you mean when you say that you want to get 
>> a bucket unlimited ?
>>  Best,
>> Oliveiros
>>
>>     ----- Original Message -----
>>      *From:* Sandeep <mailto:gibsosmat@gmail.com>
>>     *To:* pgsql-sql@postgresql.org <mailto:pgsql-sql@postgresql.org>
>>     *Sent:* Wednesday, June 24, 2009 5:39 PM
>>     *Subject:* [SQL] Bucketing Row Data in columns
>>
>>     Hi all,
>>     I need help on creating a sql, not a problem even if its pl/sql
>>
>>     I have orders table schema is as follow
>>
>>     orders(order_id,user_id, create_timestamp, amount)
>>
>>     and I want to generate a report like
>>     for the past 3 days bucketing purchases i.e SUM(amount) every day
>>     in columns
>>     i.e result will be having these columns.
>>
>>     (user_id, amount_day1, amount_day2, amount_day3)
>>
>>     ex:
>>     am leaving order_id assume they are auto incrementing and unique,
>>     date format dd/mm/yyyy
>>     (user_id, create_timestamp, amount)
>>     (user1, 01/01/2009,100)
>>     (user1, 01/01/2009,100)
>>     (user2, 01/01/2009,100)
>>     (user2, 02/01/2009,100)
>>     (user2, 02/01/2009,100)
>>     (user1, 02/01/2009,100)
>>     (user2, 03/01/2009,100)
>>     (user2, 03/01/2009,100)
>>     (user3, 03/01/2009,100)
>>
>>
>>     result
>>
>>     (user_id, amount_day1, amount_day2, amount_day3)
>>     (user1, 200, 200, 0)
>>     (user2, 100, 200, 200)
>>     (user3, 0, 0, 100)
>>
>>
>>     hope you guys got what I am trying to generate through sql.
>>
>>     I could get this data in each row, but I want it in columns.
>>     Can anyone help me on this? lets assume the buckets are fixed i.e
>>     3 only. but I wish to get them unlimited i.e day 1 to day 20.
>>
>>     Regards
>>     Sandeep Bandela
>>
>
>
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