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PostgreSQL avg()庘昄

準溊寘录桺䆹    䫌 悕垵幥 敘桄䬽橸    敟蓽庺渇

PostgreSQL䔇AVG庘昄滇䫘準欆庺劇䓉螄嘘婺䔇婔婻庖枕䔇广庺唚㔗

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婺庖䊖蓼AVG庘昄蔄荏臘COMPANY 橬套婋螄嘘

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testdb# select * from COMPANY;
 id | name  | age | address   | salary
----+-------+-----+-----------+--------
  1 | Paul  |  32 | California|  20000
  2 | Allen |  25 | Texas     |  15000
  3 | Teddy |  23 | Norway    |  20000
  4 | Mark  |  25 | Rich-Mond |  65000
  5 | David |  27 | Texas     |  85000
  6 | Kim   |  22 | South-Hall|  45000
  7 | James |  24 | Houston   |  10000
(7 rows)
 
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testdb=# SELECT AVG(SALARY) FROM COMPANY; 
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傖婪PostgreSQL䔇臘嚔库䫘傖婋䂷悩

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        avg
 ------------------
  37142.8571428571
(1 row)
 
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testdb=# SELECT name, AVG(SALARY) FROM COMPANY GROUP BY name; 
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  name  |  avg
 -------+-------
  Teddy | 20000
  Paul  | 20000
  Mark  | 65000
  David | 85000
  Allen | 15000
  Kim   | 45000
  James | 10000
(7 rows) gitbook.net
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橸桺湺鵻PostgreSQL avg()庘昄
蘸蘘臙媺䘍寘桺鷆毖:http://www.gitbook.net/html/postgresql/2013/080889.html
婪婔䇺PostgreSQL min()庘昄      婋婔䇺PostgreSQL sum()庘昄