CREATE ROLE

Name

CREATE ROLE -- 定义一个新的数据库角色

Synopsis

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_

Description

CREATE ROLE 命令用于为PostgreSQL数据库集群增加新的角色。 角色是拥有数据库对象和数据库权限的实体。一个角色可以依据其被使用的情况，被看做一个用户"user"或者一个组 "group"。 参考Chapter 20和Chapter 19这两个文档，去获取有关用户和认证管理的相关信息。 你必须要有CREATEROLE权限，或者你是一个超级用户，你才能使用 CREATE ROLE命令。

注意，角色是定义在数据库集群级别的，所以在集群中的所有数据库中都是有效的。

参数

_name_

新角色的名称。

SUPERUSER``NOSUPERUSER

这两个条件决定一个新的角色是否为一个超级用户（"superuser"），超级用户可以超越数据库内的所有访问限制。 超级用户状态是危险的，应该在真正需要的情况下才被使用。你自己必须是一个超级用户，才能创建一个新的超级用户。如果没有指定 这个条件，缺省是 NOSUPERUSER。

CREATEDB NOCREATEDB

这两个条件定义用户创建数据库的权限。如果被指定为CREATEDB，则该用户被赋予创建数据库的权限。 被指定为NOCREATEDB 将没有创建数据库的权限。如果没有指定这个条件，缺省是NOCREATEDB 。

CREATEROLE NOCREATEROLE

这两个条件决定一个角色是否被允许创建新角色（即，执行CREATE ROLE命令的权限）。 一个角色如果被赋予CREATEROLE权限，则同时也具有了修改或删除其他角色的权限。如果没有指定这个条件， 则缺省是 NOCREATEROLE。

CREATEUSER NOCREATEUSER

这两个条件是过时的，不过现在仍被数据库接受，他们和条件SUPERUSER NOSUPERUSER是等效的。 注意，他们和 CREATEROLE NOCREATEROLE并无关系。

INHERIT NOINHERIT

These clauses determine whether a role "inherits" the privileges of roles it is a member of. A role with the INHERIT attribute can automatically use whatever database privileges have been granted to all roles it is directly or indirectly a member of. Without INHERIT, membership in another role only grants the ability to SET ROLE to that other role; the privileges of the other role are only available after having done so. If not specified, INHERIT is the default.

LOGIN NOLOGIN

These clauses determine whether a role is allowed to log in; that is, whether the role can be given as the initial session authorization name during client connection. A role having the LOGIN attribute can be thought of as a user. Roles without this attribute are useful for managing database privileges, but are not users in the usual sense of the word. If not specified, NOLOGIN is the default, except when CREATE ROLE is invoked through its alternative spelling CREATE USER. 这两个参数决定一个角色是否有登进数据库的权限；一个拥有LOGIN属性的角色（role），可以被视为一个用户（user）。

REPLICATION NOREPLICATION

These clauses determine whether a role is allowed to initiate streaming replication or put the system in and out of backup mode. A role having the REPLICATION attribute is a very highly privileged role, and should only be used on roles actually used for replication. If not specified, NOREPLICATION is the default.

CONNECTION LIMIT _connlimit_

If role can log in, this specifies how many concurrent connections the role can make. -1 (the default) means no limit.

PASSWORD _password_

Sets the role's password. (A password is only of use for roles having the LOGIN attribute, but you can nonetheless define one for roles without it.) If you do not plan to use password authentication you can omit this option. If no password is specified, the password will be set to null and password authentication will always fail for that user. A null password can optionally be written explicitly as PASSWORD NULL.

ENCRYPTED UNENCRYPTED

These key words control whether the password is stored encrypted in the system catalogs. (If neither is specified, the default behavior is determined by the configuration parameter password_encryption.) If the presented password string is already in MD5-encrypted format, then it is stored encrypted as-is, regardless of whether ENCRYPTED or UNENCRYPTED is specified (since the system cannot decrypt the specified encrypted password string). This allows reloading of encrypted passwords during dump/restore.

Note that older clients might lack support for the MD5 authentication mechanism that is needed to work with passwords that are stored encrypted.

VALID UNTIL '_timestamp_'

The VALID UNTIL clause sets a date and time after which the role's password is no longer valid. If this clause is omitted the password will be valid for all time.

IN ROLE _role_name_

The IN ROLE clause lists one or more existing roles to which the new role will be immediately added as a new member. (Note that there is no option to add the new role as an administrator; use a separate GRANT command to do that.)

IN GROUP _role_name_

IN GROUP is an obsolete spelling of IN ROLE.

ROLE _role_name_

The ROLE clause lists one or more existing roles which are automatically added as members of the new role. (This in effect makes the new role a "group".)

ADMIN _role_name_

The ADMIN clause is like ROLE, but the named roles are added to the new role WITH ADMIN OPTION, giving them the right to grant membership in this role to others.

USER _role_name_

The USER clause is an obsolete spelling of the ROLE clause.

SYSID _uid_

The SYSID clause is ignored, but is accepted for backwards compatibility.

Notes

Use ALTER ROLE to change the attributes of a role, and DROP ROLE to remove a role. All the attributes specified by CREATE ROLE can be modified by later ALTER ROLE commands.

The preferred way to add and remove members of roles that are being used as groups is to use GRANT and REVOKE.

The VALID UNTIL clause defines an expiration time for a password only, not for the role per se. In particular, the expiration time is not enforced when logging in using a non-password-based authentication method.

The INHERIT attribute governs inheritance of grantable privileges (that is, access privileges for database objects and role memberships). It does not apply to the special role attributes set by CREATE ROLE and ALTER ROLE. For example, being a member of a role with CREATEDB privilege does not immediately grant the ability to create databases, even if INHERIT is set; it would be necessary to become that role via SET ROLE before creating a database.

The INHERIT attribute is the default for reasons of backwards compatibility: in prior releases of PostgreSQL, users always had access to all privileges of groups they were members of. However, NOINHERIT provides a closer match to the semantics specified in the SQL standard.

Be careful with the CREATEROLE privilege. There is no concept of inheritance for the privileges of a CREATEROLE-role. That means that even if a role does not have a certain privilege but is allowed to create other roles, it can easily create another role with different privileges than its own (except for creating roles with superuser privileges). For example, if the role "user" has the CREATEROLE privilege but not the CREATEDB privilege, nonetheless it can create a new role with the CREATEDB privilege. Therefore, regard roles that have the CREATEROLE privilege as almost-superuser-roles.

PostgreSQL includes a program createuser that has the same functionality as CREATE ROLE (in fact, it calls this command) but can be run from the command shell.

The CONNECTION LIMIT option is only enforced approximately; if two new sessions start at about the same time when just one connection "slot" remains for the role, it is possible that both will fail. Also, the limit is never enforced for superusers.

Caution must be exercised when specifying an unencrypted password with this command. The password will be transmitted to the server in cleartext, and it might also be logged in the client's command history or the server log. The command createuser, however, transmits the password encrypted. Also, psql contains a command \password that can be used to safely change the password later.

Examples

Create a role that can log in, but don't give it a password:

CREATE ROLE jonathan LOGIN;

Create a role with a password:

CREATE USER davide WITH PASSWORD 'jw8s0F4';

(CREATE USER is the same as CREATE ROLE except that it implies LOGIN.)

Create a role with a password that is valid until the end of 2004. After one second has ticked in 2005, the password is no longer valid.

CREATE ROLE miriam WITH LOGIN PASSWORD 'jw8s0F4' VALID UNTIL '2005-01-01';

Create a role that can create databases and manage roles:

CREATE ROLE admin WITH CREATEDB CREATEROLE;

Compatibility

The CREATE ROLE statement is in the SQL standard, but the standard only requires the syntax

CREATE ROLE _name_ [ WITH ADMIN _role_name_ ]

Multiple initial administrators, and all the other options of CREATE ROLE, are PostgreSQL extensions.

The SQL standard defines the concepts of users and roles, but it regards them as distinct concepts and leaves all commands defining users to be specified by each database implementation. In PostgreSQL we have chosen to unify users and roles into a single kind of entity. Roles therefore have many more optional attributes than they do in the standard.

The behavior specified by the SQL standard is most closely approximated by giving users the NOINHERIT attribute, while roles are given the INHERIT attribute.

See Also

SET ROLE, ALTER ROLE, DROP ROLE, GRANT, REVOKE, createuser