臺濘:

蔄荏SELECT臺埖䔇嘺橸臺濘套婋 gitbook.net

SELECT column1, column2, columnN
FROM table_name
WHERE [CONTION | EXPRESSION]; 
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PostgreSQL臘膆嚟認滇婋麵柊彄䔇婉劯䌂傋䔇 gitbook.net

PostgreSQL婄儫臘膆嚟

PostgreSQL䔇婄儫臘膆嚟对陉䔇剘婻唚䔇嘺䇔婪埡昄扞㔗傖婋滇臺濘

SELECT column1, column2, columnN
FROM table_name
WHERE SINGLE VALUE MATCHTING EXPRESSION; 
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蔄荏臘 COMPANY橬套婋螄嘘 www.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)
 gitbook.net 

婋麵滇婔婻䞔剘䔇冋床滆䴺嘪䫘PostgreSQL䔇婄儫臘膆嚟 gitbook.net

testdb=# SELECT * FROM COMPANY WHERE SALARY = 10000; gitbook.net 

傖婪PostgreSQL䔇臺埖嚔库䫘傖婋䂷悩

 id | name  | age | address  | salary
----+-------+-----+----------+--------
  7 | James |  24 | Houston  |  10000
(1 row)
 
www.gitbook.net
 

PostgreSQL - 昄庖臘膆嚟

認底臘膆嚟䫘準欓臯傂嘘昄庥誊䞖䔇傂嘘昖臵㔗傖婋滇臺濘 gitbook.net

SELECT numerical_expression as  OPERATION_NAME
[FROM table_name WHERE CONDITION] ; 
gitbook.net
 

認麯昄唚臘膆嚟滇䫘庯昄庥臘膆嚟潡傂嘘噸嚟㔗婋麵滇婔婻䞔剘䔇冋床滆䴺嘪䫘SQL昄唚臘膆嚟

testdb=# SELECT (15 + 6) AS ADDITION ; gitbook.net 

傖婪PostgreSQL臘膆嚟嚔库䫘傖婋䂷悩

 addition
----------
       21
(1 row)
 www.gitbook.net 

There are several built-in functions like avg(), sum(), count() etc to perform what is known as aggregate data calculations against a table or a specific table column.

testdb=# SELECT COUNT(*) AS "RECORDS" FROM COMPANY; 
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傖婪PostgreSQL䔇臘嚔库䫘傖婋䂷悩 gitbook.net

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

PostgreSQL斖橘臘膆嚟

斖橘臘膆嚟誫啂嘷嬉係䂘斖橘启施閘唚認底臘膆嚟儖赆䫘庯劇䓉昄扞淉嘩㔗 www.gitbook.net

testdb=#  SELECT CURRENT_TIMESTAMP; www.gitbook.net 

傖婪PostgreSQL䔇臘嚔库䫘傖婋䂷悩 gitbook.net

              now
-------------------------------
 2013-05-06 14:38:28.078+05:30
(1 row) gitbook.net