一、角色与用户的区别
角色就相当于岗位：角色可以是经理，助理。
用户就是具体的人：比如陈XX经理，朱XX助理，王XX助理。
在PostgreSQL 里没有区分用户和角色的概念，"CREATE USER" 为 "CREATE ROLE" 的别名，这两个命令几乎是完全相同的，唯一的区别是"CREATE USER" 命令创建的用户默认带有LOGIN属性，而"CREATE ROLE" 命令创建的用户默认不带LOGIN属性(CREATE USER is equivalent to CREATE ROLE except that CREATE USER assumes LOGIN by default, while CREATE ROLE does not)。
1.1 创建角色与用户
CREATE ROLE 语法
CREATE ROLE name [ [ WITH ] option [ ... ] ]
where option can be:
SUPERUSER | NOSUPERUSER
| CREATEDB | NOCREATEDB
| CREATEROLE | NOCREATEROLE
| CREATEUSER | NOCREATEUSER
| INHERIT | NOINHERIT
| LOGIN | NOLOGIN
| REPLICATION | NOREPLICATION
| CONNECTION LIMIT connlimit
| [ ENCRYPTED | UNENCRYPTED ] PASSWORD 'password'
| VALID UNTIL 'timestamp'
| IN ROLE role_name [, ...]
| IN GROUP role_name [, ...]
| ROLE role_name [, ...]
| ADMIN role_name [, ...]
| USER role_name [, ...]
| SYSID uid
创建david 角色和sandy 用户
postgres=# CREATE ROLE david; //默认不带LOGIN属性
CREATE ROLE
postgres=# CREATE USER sandy; //默认具有LOGIN属性
CREATE ROLE
postgres=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
david | Cannot login | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | | {}
postgres=#
postgres=# SELECT rolname from pg_roles ;
rolname
----------
postgres
david
sandy
(3 rows)
postgres=# SELECT usename from pg_user; //角色david 创建时没有分配login权限，所以没有创建用户
usename
----------
postgres
sandy
(2 rows)
postgres=#
1.2 验证LOGIN属性
postgres@CS-DEV:~> psql -U david
psql: FATAL: role "david" is not permitted to log in
postgres@CS-DEV:~> psql -U sandy
psql: FATAL: database "sandy" does not exist
postgres@CS-DEV:~> psql -U sandy -d postgres
psql (9.1.0)
Type "help" for help.
postgres=> \dt
No relations found.
postgres=>
用户sandy 可以登录，角色david 不可以登录。
1.3 修改david 的权限，增加LOGIN权限
postgres=# ALTER ROLE david LOGIN ;
ALTER ROLE
postgres=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | | {}
postgres=# SELECT rolname from pg_roles ;
rolname
----------
postgres
sandy
david
(3 rows)
postgres=# SELECT usename from pg_user; //给david 角色分配login权限，系统将自动创建同名用户david
usename
----------
postgres
sandy
david
(3 rows)
postgres=#
1.4 再次验证LOGIN属性
postgres@CS-DEV:~> psql -U david -d postgres
psql (9.1.0)
Type "help" for help.
postgres=> \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
david | | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | | {}
postgres=>
david 现在也可以登录了。
二、查看角色信息
psql 终端可以用\du 或\du+ 查看，也可以查看系统表 select * from pg_roles;
postgres=> \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
david | Cannot login | {}
postgres | Superuser, Create role, Create DB, Replication | {}
sandy | &nb