Postgresql 简明教程

PostgreSQL - SELECT Query

PostgreSQL SELECT 语句用于从数据库表中提取数据，它以结果表的形式返回数据。这些结果表称为结果集。

PostgreSQL SELECT statement is used to fetch the data from a database table, which returns data in the form of result table. These result tables are called result-sets.

Syntax

SELECT 语句的基本语法如下所示：

The basic syntax of SELECT statement is as follows −

SELECT column1, column2, columnN FROM table_name;

此处，column1、column2…是你要提取其值的表的字段。如果你想提取字段中存在的所有字段，那么可以使用以下语法 −

Here, column1, column2…are the fields of a table, whose values you want to fetch. If you want to fetch all the fields available in the field then you can use the following syntax −

SELECT * FROM table_name;

Example

考虑 COMPANY 表具有以下记录：

Consider the table COMPANY having records as follows −

 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)

以下是一个示例，它将提取 CUSTOMERS 表中存在的客户的 ID、姓名和薪酬字段 −

The following is an example, which would fetch ID, Name and Salary fields of the customers available in CUSTOMERS table −

testdb=# SELECT ID, NAME, SALARY FROM COMPANY ;

这将产生以下结果 -

This would produce the following result −

  id | name  | salary
 ----+-------+--------
   1 | Paul  |  20000
   2 | Allen |  15000
   3 | Teddy |  20000
   4 | Mark  |  65000
   5 | David |  85000
   6 | Kim   |  45000
   7 | James |  10000
(7 rows)

如果你想提取 CUSTOMERS 表的所有字段，那么使用以下查询 −

If you want to fetch all the fields of CUSTOMERS table, then use the following query −

testdb=# SELECT * FROM COMPANY;

这将产生以下结果 -

This would produce the following result −

 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)