PostgreSQL（2）常用命令（附教程）

Centos篇

1.进入退出

2.基本查看命令

3.库、表操作

4.字段类型

5.约束条件

6.INSERT语句

7.SELECT语句

8.WHERE语句

9.数据抽出选项

10.统计抽出数据

11.方便函数

12.更新和删除

13.变更表结构

14.操作多个表

15.视图

16.事务

windows篇

1.建立数据库连接

2.访问数据库

学习postgresql数据库视频学习笔记

链接B站小马视频：

【小马技术】PostgreSql 关系型数据库入门_哔哩哔哩_bilibili

Centos篇

1.进入退出

#进入postgres账户

su postgres

#退出（回到root账号）

su root

#输入密码（如果有）

2.基本查看命令

#查看数据库（账号目录下有效）

psql -l

#查看数据表（数据库目录下有效）

\dt

3.库、表操作

#建库

createdb komablog

#查看数据库

psql -l

#进入数据库

psql komablog

#建表

create table post (title varchar(255),content text);

#查看数据表

\dt

#查看数据库表信息

\d posts

#改表

alter table posts rename to komaposts;

#查看数据表

\dt

#删表

drop table komaposts;

#退出

#建立sql文件（复用建表操作）

nano db.sql

...

create table posts (title varchar(255),content text);

...

psql komablog

\i db.sql

4.字段类型

数值型：

interger（int）

real

serial

文字型：

char

varchar

text

布尔型：

boolean

日期型：

date

time

timestamp

特色类型：

array

网络地址型（inet）

JSON型

XML型

5.约束条件

not null;不能为空

unique：在所有数据中唯一

check：字段设置条件

default：字段默认值

primary key(not null,unique):主键，不能为空，且唯一不重复

6.INSERT语句

insert into [table name] (filed,...) values (value,...)

insert int posts(title,content) values (‘title2’,’content2’);

7.SELECT语句

select filed1,filed2... from [tablename]

8.WHERE语句

select * from users where score>20;

select * from users where score<30;

select * from users where score>20 and score <30;

select * from users where team=’勇士’;

select * from users where team!=’勇士’;

select * from users where player like ‘阿%’;

select * from users where player like ‘阿_’;

9.数据抽出选项

order by //排序

limit //限制前几条

offset //偏移量

select * from users order by score asc;

select * from users order by score desc;

select * from users order by team;

select * from users order by team ,score;

select * from users order by team ,score desc;

select * from users order by team desc,score desc;

select * from users order by score desc limit 3;

select * from users order by score desc limit 3 offset 1;

select * from users order by score desc limit 3 offset 2;

select * from users order by score desc limit 3 offset 3;

10.统计抽出数据

distinct

sum

max/min

group by/having //having 是针对group by 的限制关键词

select distinct team from users;

select sum(score) from users;

select max(score) from users;

select min(score) from users;

select * from users where score=(select max(score) from users);

select * from users where score=(select mim(score) from users);

select team, max(score)from users group by team;

select team, max(score) from users group by team having max(score)>=25;

select team, max(score) from users group by team having max(score)>=25 order by max(score);

11.方便函数

length //长度

concat //链接两个字符串

alias //起别名

substring //切割字符串

random //随机函数

select player,length(player) from users;

select player,concat(player,’/’,team)from users;

select player,concat(player,’/’,team) as “球员信息” from users;

select substring(team,1,1)as’球队首文字’ from users;

select concat(‘我’,substring(team,1,1))as’球队首文字’from users;

select random();

select *from users order by random();

select *from users order by random() limit 1;

Q：

concat 中的‘’在word中无法直接粘贴命令执行
as 后起别名需要用“”而不是‘’

12.更新和删除

update [table] set [filed=newvalue,...]where ...

delete from [table] where ...

update users set score =29.1 where player =’阿詹’;

update users set score=score+1 where team=’勇士’;

update users set score=score+100 where team in (‘勇士’,’骑士’);

delete from users where score >30;

13.变更表结构

alter table [tablename]...

create index ...

drop index...

\d users;

alter table users add fullname varchar(255);

\d users;

alter table users drop fullname;

\d users;

alter table users rename player to nba_player;

\d users;

alter table users alter nab_player type varchar(100);

\d users;

create index nba_player_index on users(nba_player);

\d users;

drop index nba_player_index;

14.操作多个表

select * from users;

select * from twitters;

select users.player,twitters.content from users,twitters where users.id=twitters.user_id;

select u.player,t.content from users as u,twitters as t where u.id=t.user_id;

select u.player,t.content from users as u,twitters as t where u.id=t.user_id and u.id=1;

15.视图

create view

drop view

select users.player,twitters.content from users,twitters where users.id=twitters.user_id;

create view curry_twitters as select u.player,t.content from users as u,twitters as t where u.id=t.id;

\dv

\d curry_twitters

select * from curry_twitters;

drop view curry_twitters;

\dv

16.事务

begin

commit

rollback

begin

sql1

sql2

...

commit

begin

sql1

sql2

...

rollback

windows篇

1.建立数据库连接

#接入PostgreSQL数据库

psql -h IP地址 -p 端口 -U 数据库名

（之后会要求输入数据库密码）

2.访问数据库

1、列举数据库：\l
2、选择数据库：\c 数据库名
3、查看该某个库中的所有表：\dt
4、切换数据库：\c interface
5、查看某个库中的某个表结构：\d 表名
6、查看某个库中某个表的记录：select * from apps limit 1;
7、显示字符集：\encoding
8、退出psgl：\q