Re: query question

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От Sachin Srivastava
Тема Re: query question
Дата
Msg-id 312CEA55-8D41-4AAD-891E-9CD4424859F0@enterprisedb.com
обсуждение исходный текст
Ответ на query question  (pg noob <pgnube@gmail.com>)
Список pgsql-novice
SELECT MAX(id) AS id , col1, MAX(col2) AS col2,  MAX(col3) AS col3  FROM tablename  GROUP BY col1

On Sep 16, 2011, at 7:00 PM, pg noob wrote:


Hi all,

Is there an efficient way to select the set of rows which have the max values across multiple columns?

For example given this list of data,

id_    | col1        |  col2            | col3
-------+-------------+------------------+-----------------
 19657 |          10 | 1316114172563817 |               4
 19656 |          10 | 1316114172563817 |               3
    24 |          12 | 1315847688545745 |               0
 19644 |          13 | 1316114172563817 |               0
    26 |          14 | 1315847688545745 |               0
 19646 |          15 | 1316114172563817 |               0
 19582 |          15 | 1316112258713414 |               0
 18269 |          15 | 1316023202508054 |               0
   199 |          15 | 1315936801616950 |               0
    37 |          15 | 1315847702117357 |               0
 19648 |          16 | 1316114172563817 |               0
 19583 |          16 | 1316112258713414 |               0
 18272 |          16 | 1316023202508054 |               0
   202 |          16 | 1315936801616950 |               0
    38 |          16 | 1315847702117357 |               0
 19652 |          17 | 1316114172563817 |               0
 19585 |          17 | 1316112258713414 |               0
 18276 |          17 | 1316023202508054 |               0
   206 |          17 | 1315936801616950 |               0
    39 |          17 | 1315847702117357 |               0

I would like to select the set of rows grouped by col1 which has first the highest value for col2 and second the highest value for col3.

The result set should include:

19657 |          10 | 1316114172563817 |               4
     24 |          12 | 1315847688545745 |               0
19644 |          13 | 1316114172563817 |               0
     26 |          14 | 1315847688545745 |               0
19646 |          15 | 1316114172563817 |               0
19648 |          16 | 1316114172563817 |               0
19652 |          17 | 1316114172563817 |               0

Thank you.



--
Regards,
Sachin Srivastava

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