PostgreSQL快速入门：psql工具的使用

一、psql介绍

psql是PostgreSQL中的一个命令行交互式客户端工具，类似Oracle中的命令行工具sqlplus:

1.允许你交互地键入SQL或命令，然后把它们发出给PostgreSQL服务器，再显示SQL或命令的结果；

2.输入的内容还可以来自一个文件；

3.还提供了一些元命令和多种类似shell的特性来实现书写脚本，以及对对量任务的自动化工作；

二、psql的简单实用

按照前面的步骤，切换su - postgres用户，实用psql工具连接数据库。

1.查看有哪些数据库

postgres=# \l
                                  List of databases
   Name    |  Owner   | Encoding |  Collation  |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres : postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres : postgres=CTc/postgres
(3 rows) 

a.安装好后，默认会有一个叫postgres的数据库，还有两个模板数据库template0和template1；

b.用户再建数据库的时候，默认是从模板数据库template1克隆出来；

c.template0是一个最简化的模板库，创建数据库时，如果明确指定从此数据库集成，将创建一个最简化的数据库；

2.创建数据库osdba

postgres=# CREATE DATABASE osdba;
CREATE DATABASE
postgres-# \l
                                  List of databases
   Name    |  Owner   | Encoding |  Collation  |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 osdba     | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres : postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres : postgres=CTc/postgres
(4 rows) 

3.访问osdba数据库

-bash-4.1$ psql osdba
psql (8.4.20)
Type "help" for help. 

4.在数据库osdba中创建表t

osdba=# create table t(id int primary key,name varchar(40));
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t_pkey" for table "t"
CREATE TABLE 

5.查看osdb数据库中的表

osdba=# \d
        List of relations
 Schema | Name | Type  |  Owner
--------+------+-------+----------
 public | t    | table | postgres
(1 row) 

6.创建数据库testdb后，并连接到testdb数据库

osdba=# CREATE DATABASE testdb;
CREATE DATABASE
osdba=# \c testdb
psql (8.4.20)
You are now connected to database "testdb".
testdb=#  

三、psql的常用命令

1.\d命令-查看当前数据库中的所有表

osdba-# \d
        List of relations
 Schema | Name | Type  |  Owner
--------+------+-------+----------
 public | t    | table | postgres
(1 row) 

2.\d命令-跟一个表命，查看这个表的结构定义

osdba-# \d t
              Table "public.t"
 Column |         Type          | Modifiers
--------+-----------------------+-----------
 id     | integer               | not null
 name   | character varying(40) |
Indexes:
    "t_pkey" PRIMARY KEY, btree (id) 

3.\d命令-可以查看表格t的索引信息

osdba-# \d t_pkey
Index "public.t_pkey"
 Column |  Type
--------+---------
 id     | integer
primary key, btree, for table "public.t" 

4.\d命令-跟通配符如*或？

osdba-# \d t*
              Table "public.t"
 Column |         Type          | Modifiers
--------+-----------------------+-----------
 id     | integer               | not null
 name   | character varying(40) |
Indexes:
    "t_pkey" PRIMARY KEY, btree (id) 

Index "public.t_pkey"
 Column |  Type
--------+---------
 id     | integer
primary key, btree, for table "public.t" 

5.\d+命令，显示比\d命令更加详细的信息，显示与表列关联的注释

osdba-# \d+
                    List of relations
 Schema | Name | Type  |  Owner   |  Size   | Description
--------+------+-------+----------+---------+-------------
 public | t    | table | postgres | 0 bytes |
(1 row) 

6.匹配不同对象类型的\d命令，如\dt-只想显示匹配的表；\di-只想显示索引；\ds-只显示序列；\dv-只显示视图；\df-只显示函数等...

osdba-# \dt t*
        List of relations
 Schema | Name | Type  |  Owner
--------+------+-------+----------
 public | t    | table | postgres 

7.\dn命令-列出所有的schema

osdba-# \dn
        List of schemas
        Name        |  Owner
--------------------+----------
 information_schema | postgres
 pg_catalog         | postgres
 pg_toast_temp_1    | postgres
 public             | postgres
(5 rows) 

8.\db命令-显示所有表空间

osdba-# \db
       List of tablespaces
    Name    |  Owner   | Location
------------+----------+----------
 pg_default | postgres |
 pg_global  | postgres |
(2 rows) 

9.\dg-列出数据库中所有角色和用户

osdba-# \dg
            List of roles
 Role name | Attributes  | Member of
-----------+-------------+-----------
 postgres  | Superuser   | {}
           : Create role
           : Create DB  

10.\dp-显示表的权限分配情况

osdba-# \dp
                          Access privileges
 Schema | Name | Type  | Access privileges | Column access privileges
--------+------+-------+-------------------+--------------------------
 public | t    | table |                   |
(1 row) 

四、指定字符集编译的命令

1.\encoding gbk-设置客户端的字符编码为gbk

五、\pset命令

1.\pset命令-用于设置输出的格式，\pset border 0/1/2：输出内容无边框、只有内边框、内外都有边框 

osdba-# \pset border 0
Border style is 0.
osdba-# \dp
                     Access privileges
Schema Name Type  Access privileges Column access privileges
------ ---- ----- ----------------- ------------------------
public t    table
(1 row) 

osdba-# \pset border 1
Border style is 1.
osdba-# \dp
                          Access privileges
 Schema | Name | Type  | Access privileges | Column access privileges
--------+------+-------+-------------------+--------------------------
 public | t    | table |                   |
(1 row) 

osdba-# \pset border 2
Border style is 2.
osdba-# \dp
                           Access privileges
+--------+------+-------+-------------------+--------------------------+
| Schema | Name | Type  | Access privileges | Column access privileges |
+--------+------+-------+-------------------+--------------------------+
| public | t    | table |                   |                          |
+--------+------+-------+-------------------+--------------------------+
(1 row) 

2.\x命令-可以把表中的每一行的每列数据都拆分为单行展示，如果有一行数据有太多的拆行，显示不下，就可以使用这个命令

osdba-# \x
Expanded display is on.
osdba-# \dp
Access privileges
+-[ RECORD 1 ]-------------+--------+
| Schema                   | public |
| Name                     | t      |
| Type                     | table  |
| Access privileges        |        |
| Column access privileges |        |
+--------------------------+--------+ 

osdba-# \x
Expanded display is off.
osdba-# \dp
                           Access privileges
+--------+------+-------+-------------------+--------------------------+
| Schema | Name | Type  | Access privileges | Column access privileges |
+--------+------+-------+-------------------+--------------------------+
| public | t    | table |                   |                          |
+--------+------+-------+-------------------+--------------------------+
(1 row) 

五、psql使用技巧

1.使用上下键把过去使用过的命令或者SQL语句调出来，连续两个tab键表示补全或给出提示输入

osdba-# \d
\d    \dc   \dD   \dew  \dFd  \dg   \dn   \ds   \dT
\da   \dC   \des  \df   \dFp  \di   \do   \dS   \du
\db   \dd   \deu  \dF   \dFt  \dl   \dp   \dt   \dv   

2.psql加上-E参数，可以把psql中各种以"\"开头的命令执行的实际SQL打印出来

-bash-4.1$ psql -E postgres
psql (8.4.20)
Type "help" for help. 

postgres=# \d
********* QUERY **********
SELECT n.nspname as "Schema",
  c.relname as "Name",
  CASE c.relkind WHEN ‘r‘ THEN ‘table‘ WHEN ‘v‘ THEN ‘view‘ WHEN ‘i‘ THEN ‘index‘ WHEN ‘S‘ THEN ‘sequence‘ WHEN ‘s‘ THEN ‘special‘ END as "Type",
  pg_catalog.pg_get_userbyid(c.relowner) as "Owner"
FROM pg_catalog.pg_class c
     LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind IN (‘r‘,‘v‘,‘S‘,‘‘)
      AND n.nspname <> ‘pg_catalog‘
      AND n.nspname <> ‘information_schema‘
      AND n.nspname !~ ‘^pg_toast‘
  AND pg_catalog.pg_table_is_visible(c.oid)
ORDER BY 1,2;
************************** 

No relations found 

如果你在使用之后，想立即关闭

postgres=# \set ECHO_HIDDEN off
postgres=# \d
No relations found. 

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