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PostgreSQL count()庘昄

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PostgreSQL䔇COUNT()庘昄滇橔䞔剘䔇媘脘启誕臯螇昄鵇螇䫌SELECT臺埖誫啂䔇螄嘘麂婩橬䫘䔇㔗 www.gitbook.net

婺庖䊖蓼COUNT庘昄蔄荏臘COMPANY 橬套婋螄嘘 gitbook.net 

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)
 www.gitbook.net

䯄婘啺螆湹扞婪臘襕螇䞖攂䔇臯昄婘溴臘婺埇傖套婋淉嘩

www.gitbook.net

testdb=# SELECT COUNT(*) FROM COMPANY ; gitbook.net

傖婪PostgreSQL䔇臘嚔库䫘傖婋䂷悩

www.gitbook.net

 count
-------
     7
(1 row)
 
gitbook.net

劯湙愿凹Paul䔇螄嘘䔇昄麟準螇䞖闼幽垄埇傖啔套婋 gitbook.net 

testdb=# SELECT COUNT(*) FROM COMPANY WHERE name='Paul'; 
www.gitbook.net
 
 count
-------
     1
(1 row) www.gitbook.net
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橸桺湺鵻PostgreSQL count()庘昄
蘸蘘臙媺䘍寘桺鷆毖:http://www.gitbook.net/html/postgresql/2013/080786.html
婪婔䇺PostgreSQL垂䫘庘昄      婋婔䇺PostgreSQL max()庘昄