Re: Creating Report for PieChart

On Tue, Oct 13, 2015 at 9:14 PM, Scott Mead <scottm@openscg.com> wrote:

On Oct 13, 2015, at 19:56, Alex Magnum <magnum11200@gmail.com> wrote:

Hello,

I need to process some statistics for a pie chart (json) where I only want to show a max of 8 slices. If I have more data points like in below table I need to combine all to a slice called others. If there are less or equal 8 i use them as is.

I am currently doing this with a plperl function which works well but was just wondering out of curiosity if that could be done withing an sql query.

Anyone having done something similar who could point me in the right direction? 

SELECT count(*),country_name FROM stats_archive WHERE id=400 GROUP BY country_name ORDER BY COUNT DESC;

 count |   country_name

-------+-------------------

   302 | Malaysia

    65 | Singapore

    57 | Thailand

    26 | Indonesia

    15 | France

    14 | United States

    14 | India

    13 | Philippines

    12 | Vietnam

    10 | Republic of Korea

    10 | Canada

     7 | Australia

     6 | Brazil

     6 | Czech Republic

     5 | Switzerland

     4 | Saudi Arabia

     3 | Ireland

     3 | Japan

     3 | Sweden

     3 | South Africa

     3 | Belarus

     3 | Colombia

     3 | United Kingdom

     1 | Peru

   country_name  | count | perc  

-----------------+-------+-------

 Malaysia        |   302 |  51.4 

 Singapore       |    65 |  11.0 

 Thailand        |    57 |   9.7 

 Indonesia       |    26 |   4.4 

 France          |    15 |   2.6 

 United States   |    14 |   2.4 

 India           |    14 |   2.4 

 Others          |    95 |  16.1 

 Total           |   588 |   100 

Thanks a lot for any suggestions

I would use rank to get a rank number for each record. 

  Sorry, Sent the last one from my phone, here's an example:

Use 'rank' to generate the rank order of the entry.

postgres=# select country, count(1) num_entries, 

            rank() over (order by count(1) DESC)

            from test GROUP by country ORDER BY num_entries DESC;

 country | num_entries | rank

---------+-------------+------

 US      |          20 |    1

 CA      |          15 |    2

 SP      |           8 |    3

 IT      |           7 |    4

(4 rows)

There's probably an easier way to do this without a sub-select, but, it works.  

postgres=# SELECT country, num_entries, rank 

   FROM (select country, count(1) num_entries,

   rank() over (order by count(1) DESC)

   FROM test GROUP by country

) foo WHERE rank < 4;

 country | num_entries | rank

---------+-------------+------

 US      |          20 |    1

 CA      |          15 |    2

 SP      |           8 |    3

(3 rows)

postgres=# 

--

Scott Mead

OpenSCG

www.openscg.com

Alex