Ở bài viết trước hướng dẫn các bạn cách sao chép dữ liệu của bảng. Trong bài viết này sẽ hướng dẫn các bạn sao chép database trong cùng 1 server hoặc từ 2 server khác nhau. Các bước để sao chép database: Ví dụ, chúng ta sao chép database Trước tiên cần truy cập vào MySQL database server:Sao chép database trong cùng server
CREATE DATABASE
mysqldump
để xuất toàn bộ
dữ liệu của database mà bạn muốn sao chép.classicmodels
vào database mới classicmodels_backup
.Bước 1. Tạo mới database
classmodels_backup
:>mysql -u root -p
Enter password: **********
Sau đó tạo database:
> CREATE DATABASE classicmodels_backup;
Xem lại danh sách database cho chắc:
Kết quả:
+----------------------+
| Database |
+----------------------+
| classicmodels |
| classicmodels_backup |
| information_schema |
| mysql |
| performance_schema |
| sys |
+----------------------+
6 rows in set [0.00 sec]
Bước 2: Sử dụng mysqldump
để xuất dữ liệu
Giả sử bạn muốn xuất dữ liệu database classicmodels
ra 1 file SQL và lưu tại thư mục D:\db
:
>mysqldump -u root -p classicmodels > d:\db\classicmodels.sql
Enter password: **********
Chú ý: Dấu >
để chỉ export.
Bước 3: Import file d:\db\classicmodels.sql
vào database classicmodels_backup.
>mysql -u root -p classicmodels_backup < d:\db\classicmodels.sql
Enter password: **********
Chú ý: Dấu SHOW TABLES FROM classicmodels_backup;
Kết quả:
+--------------------------------+
| Tables_in_classicmodels_backup |
+--------------------------------+
| customers |
| employees |
| offices |
| orderdetails |
| orders |
| payments |
| productlines |
| products |
+--------------------------------+
8 rows in set [0.01 sec]
Sao chép database từ 2 server khác nhau
Các bước thực hiện:
- Export database từ server nguồn vào 1 file SQL.
- Sao chép SQL file ở bước 1 sang server đích.
- Import SQL file vào server đích.
Ví dụ thực hiện sao chép database classicmodels
sang server khác.
Bước
1: Export database classicmodels
ra file db.sql
.
>mysqldump -u root -p --databases classicmodels > d:\db\db.sql
Enter password: **********
Chú ý option --database
cho phép chạy đồng thời 2 lệnh CREATE DATABASE
và USE
.
Hai lệnh sau tương đương với option --database
CREATE DATABASE `classicmodels`.
USE `classicmodels`;
Bước 2: Giả sử file SQL db.sql
được copy vào thư mục c:\tmp\
của server đích.
Bước 3: Import file SQL
>mysql -u root -p classicmodels < c:\tmp\db.sql
Bài viết hướng dẫn sử dụng công cụ
mysqldump
để xuất dữ liệu database. Hi vọng bài viết hữu ích cho bác bạn.
Hãy like, share và comment để cùng nhau học tập nhé.
13.7.1.6 GRANT Statement
GRANT
priv_type [[column_list]]
[, priv_type [[column_list]]] ...
ON [object_type] priv_level
TO user_or_role [, user_or_role] ...
[WITH GRANT OPTION]
[AS user
[WITH ROLE
DEFAULT
| NONE
| ALL
| ALL EXCEPT role [, role ] ...
| role [, role ] ...
]
]
}
GRANT PROXY ON user_or_role
TO user_or_role [, user_or_role] ...
[WITH GRANT OPTION]
GRANT role [, role] ...
TO user_or_role [, user_or_role] ...
[WITH ADMIN OPTION]
object_type: {
TABLE
| FUNCTION
| PROCEDURE
}
priv_level: {
*
| *.*
| db_name.*
| db_name.tbl_name
| tbl_name
| db_name.routine_name
}
user_or_role: {
user [see Section 6.2.4, “Specifying Account Names”]
| role [see Section 6.2.5, “Specifying Role Names”]
}
The GRANT
statement assigns privileges and roles to MySQL user accounts and roles. There are several aspects to the GRANT
statement, described under the following
topics:
GRANT General Overview
Object Quoting Guidelines
Account Names
Privileges Supported by MySQL
Global Privileges
Database Privileges
Table Privileges
Column Privileges
Stored Routine Privileges
Proxy User Privileges
Granting Roles
The
AS
Clause and Privilege RestrictionsOther Account Characteristics
MySQL and Standard SQL Versions of GRANT
The GRANT
statement enables system administrators to grant privileges and roles, which can be granted to user accounts and roles. These syntax restrictions apply:
GRANT
cannot mix granting both privileges and roles in the same statement. A givenGRANT
statement must grant either privileges or roles.The
ON
clause distinguishes whether the statement grants privileges or roles:With
ON
, the statement grants privileges.Without
ON
, the statement grants roles.It is permitted to assign both privileges and roles to an account, but you must use separate
GRANT
statements, each with syntax appropriate to what is to be granted.
For more information about roles, see Section 6.2.10, “Using Roles”.
To grant a privilege with GRANT
, you must have the GRANT OPTION
privilege, and you must have the privileges that you are granting. [Alternatively, if you have the
UPDATE
privilege for the grant tables in the mysql
system schema, you can grant any account any privilege.] When the read_only
system variable is enabled,
GRANT
additionally requires the CONNECTION_ADMIN
privilege [or the deprecated SUPER
privilege].
GRANT
either succeeds for all named users and roles or rolls back and has no effect if any error occurs. The statement is written to the binary log only if it succeeds for all named users and roles.
The REVOKE
statement is related to
GRANT
and enables administrators to remove account privileges. See Section 13.7.1.8, “REVOKE Statement”.
Each account name uses the format described in Section 6.2.4, “Specifying Account Names”. Each role name uses the format described in Section 6.2.5, “Specifying Role Names”. For example:
GRANT ALL ON db1.* TO 'jeffrey'@'localhost';
GRANT 'role1', 'role2' TO 'user1'@'localhost', 'user2'@'localhost';
GRANT SELECT ON world.* TO 'role3';
The host name part of the account or role name, if omitted, defaults to '%'
.
Normally, a database administrator first uses CREATE USER
to create an account and define its nonprivilege characteristics such as its password, whether it uses secure connections, and limits on access to server resources, then uses GRANT
to define its
privileges. ALTER USER
may be used to change the nonprivilege characteristics of existing accounts. For example:
CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'password';
GRANT ALL ON db1.* TO 'jeffrey'@'localhost';
GRANT SELECT ON db2.invoice TO 'jeffrey'@'localhost';
ALTER USER 'jeffrey'@'localhost' WITH MAX_QUERIES_PER_HOUR 90;
From the mysql program,
GRANT
responds with Query OK, 0 rows affected
when executed successfully. To determine what privileges result from the operation, use SHOW GRANTS
. See
Section 13.7.7.21, “SHOW GRANTS Statement”.
Important
Under some circumstances, GRANT
may be recorded in server logs or on the client side in a history file such as ~/.mysql_history
, which means that cleartext passwords may be read by
anyone having read access to that information. For information about the conditions under which this occurs for the server logs and how to control it, see Section 6.1.2.3, “Passwords and Logging”. For similar information about client-side logging, see Section 4.5.1.3, “mysql Client Logging”.
GRANT
supports host names up to 255 characters long [60 characters prior to MySQL 8.0.17]. User names can be up to 32 characters. Database, table, column, and routine names can be up to 64 characters.
Warning
Do not attempt to change the permissible length for user names by
altering the mysql.user
system table. Doing so results in unpredictable behavior which may even make it impossible for users to log in to the MySQL server. Never alter the structure of tables in the mysql
system schema in any manner except by means of the procedure described in Section 2.11, “Upgrading MySQL”.
Several objects within GRANT
statements are subject to quoting, although quoting is optional in many cases: Account, role, database, table, column, and routine names. For example, if a user_name
or host_name
value in an account name is legal as an unquoted identifier, you need not quote it.
However, quotation marks are necessary to specify a user_name
string containing special characters [such as -
], or a host_name
string containing special characters or wildcard characters such as %
[for example, 'test-user'@'%.com'
]. Quote the user name and host name separately.
To specify quoted values:
Quote database, table, column, and routine names as identifiers.
Quote user names and host names as identifiers or as strings.
Quote passwords as strings.
For string-quoting and identifier-quoting guidelines, see Section 9.1.1, “String Literals”, and Section 9.2, “Schema Object Names”.
The _
and %
wildcards are
permitted when specifying database names in GRANT
statements that grant privileges at the database level [GRANT ... ON
]. This means, for example, that to use a db_name
.*_
character as part of a database name, specify it using the \
escape character as \_
in the GRANT
statement, to prevent the user from being able to access additional databases matching the wildcard pattern [for example, GRANT ... ON `foo\_bar`.* TO ...
].
In privilege assignments, MySQL interprets occurrences of unescaped _
and %
SQL wildcard characters in database names as literal characters under these circumstances:
When a database name is not used to grant privileges at the database level, but as a qualifier for granting privileges to some other object such as a table or routine [for example,
GRANT ... ON
].db_name
.tbl_name
Enabling
partial_revokes
causes MySQL to interpret unescaped_
and%
wildcard characters in database names as literal characters, just as if they had been escaped as\_
and\%
. Because this changes how MySQL interprets privileges, it may be advisable to avoid unescaped wildcard characters in privilege assignments for installations wherepartial_revokes
may be enabled. For more information, see Section 6.2.12, “Privilege Restriction Using Partial Revokes”.
A user
value in a GRANT
statement indicates a MySQL account to which the statement applies. To accommodate granting rights to users from arbitrary hosts, MySQL supports specifying the user
value in the form '
. user_name
'@'host_name
'
You can
specify wildcards in the host name. For example, '
applies to user_name
'@'%.example.com'user_name
for any host in the example.com
domain, and '
applies to user_name
'@'198.51.100.%'user_name
for any host in the 198.51.100
class C subnet.
The simple form '
is a synonym for user_name
''
. user_name
'@'%'
MySQL does not support wildcards in user names. To refer to an anonymous user, specify an account with an empty
user name with the GRANT
statement:
GRANT ALL ON test.* TO ''@'localhost' ...;
In this case, any user who connects from the local host with the correct password for the anonymous user is permitted access, with the privileges associated with the anonymous-user account.
For additional information about user name and host name values in account names, see Section 6.2.4, “Specifying Account Names”.
Warning
If you permit local anonymous users to connect to the MySQL server, you should also grant privileges to all local users as '
. Otherwise, the anonymous user account for user_name
'@'localhost'localhost
in the mysql.user
system table is used when named users try to log in to the MySQL
server from the local machine. For details, see Section 6.2.6, “Access Control, Stage 1: Connection Verification”.
To determine whether this issue applies to you, execute the following query, which lists any anonymous users:
SELECT Host, User FROM mysql.user WHERE User='';
To avoid the problem just described, delete the local anonymous user account using this statement:
DROP USER ''@'localhost';
Privileges Supported by MySQL The following tables summarize the permissible static and dynamic priv_type
privilege types that can be specified for the GRANT
and
REVOKE
statements, and the levels at which each privilege can be granted. For additional information about each privilege, see Section 6.2.2, “Privileges Provided by MySQL”. For information about the differences between static and dynamic
privileges, see Static Versus Dynamic Privileges.
Table 13.11 Permissible Static Privileges for GRANT and REVOKE
ALL [PRIVILEGES]
| Grant all privileges at specified access level except GRANT OPTION and PROXY .
|
ALTER
| Enable use of ALTER TABLE . Levels: Global, database, table.
|
ALTER ROUTINE
| Enable stored routines to be altered or dropped. Levels: Global, database, routine. |
CREATE
| Enable database and table creation. Levels: Global, database, table. |
CREATE ROLE
| Enable role creation. Level: Global. |
CREATE ROUTINE
| Enable stored routine creation. Levels: Global, database. |
CREATE TABLESPACE
| Enable tablespaces and log file groups to be created, altered, or dropped. Level: Global. |
CREATE TEMPORARY TABLES
| Enable use of CREATE
TEMPORARY TABLE . Levels: Global, database.
|
CREATE USER
| Enable use of CREATE USER , DROP USER , RENAME USER , and
REVOKE ALL
PRIVILEGES . Level: Global.
|
CREATE VIEW
| Enable views to be created or altered. Levels: Global, database, table. |
DELETE
| Enable use of DELETE . Level: Global, database, table.
|
DROP
| Enable databases, tables, and views to be dropped. Levels: Global, database, table. |
DROP ROLE
| Enable roles to be dropped. Level: Global. |
EVENT
| Enable use of events for the Event Scheduler. Levels: Global, database. |
EXECUTE
| Enable the user to execute stored routines. Levels: Global, database, routine. |
FILE
| Enable the user to cause the server to read or write files. Level: Global. |
GRANT OPTION
| Enable privileges to be granted to or removed from other accounts. Levels: Global, database, table, routine, proxy. |
INDEX
| Enable indexes to be created or dropped. Levels: Global, database, table. |
INSERT
| Enable use of INSERT . Levels: Global, database, table, column.
|
LOCK TABLES
| Enable use of LOCK TABLES on tables for which you have the SELECT privilege. Levels: Global, database.
|
PROCESS
| Enable the user to see all processes with SHOW
PROCESSLIST . Level: Global.
|
PROXY
| Enable user proxying. Level: From user to user. |
REFERENCES
| Enable foreign key creation. Levels: Global, database, table, column. |
RELOAD
| Enable use of FLUSH operations. Level:
Global.
|
REPLICATION CLIENT
| Enable the user to ask where source or replica servers are. Level: Global. |
REPLICATION SLAVE
| Enable replicas to read binary log events from the source. Level: Global. |
SELECT
| Enable use of SELECT . Levels: Global, database, table, column.
|
SHOW DATABASES
| Enable SHOW DATABASES to show all databases. Level: Global.
|
SHOW VIEW
| Enable use of SHOW CREATE VIEW . Levels: Global, database, table.
|
SHUTDOWN
| Enable use of mysqladmin shutdown. Level: Global. |
SUPER
| Enable use of other administrative operations such as CHANGE REPLICATION SOURCE
TO , CHANGE MASTER
TO , KILL ,
PURGE BINARY LOGS , SET
GLOBAL , and mysqladmin debug
command. Level: Global.
|
TRIGGER
| Enable trigger operations. Levels: Global, database, table. |
UPDATE
| Enable use of UPDATE . Levels: Global, database, table, column.
|
USAGE
| Synonym for “no privileges” |
A trigger is associated with a table. To create or drop a trigger, you must have the TRIGGER
privilege for the table, not the trigger.
In GRANT
statements, the
ALL
[PRIVILEGES]
or PROXY
privilege must be named by itself and cannot be specified along with other privileges. ALL
[PRIVILEGES]
stands for all privileges available for the level at which privileges
are to be granted except for the GRANT OPTION
and PROXY
privileges.
MySQL account information is stored in the tables of the mysql
system schema. For additional details, consult
Section 6.2, “Access Control and Account Management”, which discusses the mysql
system schema and the access control system extensively.
If the grant tables hold privilege rows that contain mixed-case database or table names and the
lower_case_table_names
system variable is set to a nonzero value, REVOKE
cannot be used to revoke these privileges. It is necessary in such cases to manipulate the grant tables directly.
[GRANT
does not create such rows when lower_case_table_names
is set, but such rows might have been created prior to setting that variable. The
lower_case_table_names
setting can only be configured at server startup.]
Privileges can be granted at several levels, depending on the syntax used for the ON
clause. For REVOKE
, the same ON
syntax specifies which
privileges to remove.
For the global, database, table, and routine levels, GRANT ALL
assigns only the privileges that exist at the level you are granting. For example, GRANT ALL ON
is a database-level statement, so it does not grant any global-only privileges such as
db_name
.*FILE
. Granting ALL
does not assign the GRANT OPTION
or
PROXY
privilege.
The object_type
clause, if present, should be specified as TABLE
, FUNCTION
, or PROCEDURE
when the following object is a table, a stored function, or a stored procedure.
The privileges that a user holds for a database, table, column, or routine are formed additively as the logical
OR
of the account privileges at each of the privilege levels, including the global level. It is not possible to deny a privilege granted at a higher level by absence of that privilege at a lower level. For example, this statement grants the SELECT
and
INSERT
privileges globally:
GRANT SELECT, INSERT ON *.* TO u1;
The globally granted privileges apply to all databases, tables, and columns, even though not granted at any of those lower levels.
As of MySQL 8.0.16, it is possible to explicitly deny a privilege granted at the global level by revoking it for particular databases, if the
partial_revokes
system variable is enabled:
GRANT SELECT, INSERT, UPDATE ON *.* TO u1;
REVOKE INSERT, UPDATE ON db1.* FROM u1;
The result of the preceding statements is that SELECT
applies globally to all tables, whereas INSERT
and UPDATE
apply globally except to tables in db1
. Account access to db1
is read only.
Details of the privilege-checking procedure are presented in Section 6.2.7, “Access Control, Stage 2: Request Verification”.
If you are using table, column, or routine privileges for even one user, the server examines table, column, and routine privileges for all users and this slows down MySQL a bit. Similarly, if you limit the number of queries, updates, or connections for any users, the server must monitor these values.
MySQL enables you to grant privileges on databases or tables that do not exist. For tables, the privileges to be granted must include the
CREATE
privilege. This behavior is by design, and is intended to enable the database administrator to prepare user accounts and privileges for databases or tables that are to be created at a later time.
Important
MySQL does not automatically revoke any privileges when you drop a database or table. However, if you drop a routine, any routine-level privileges granted for that routine are revoked.
Global Privileges Global privileges are administrative or apply to all databases on a given server. To assign global privileges, use ON *.*
syntax:
GRANT ALL ON *.* TO 'someuser'@'somehost';
GRANT SELECT, INSERT ON *.* TO 'someuser'@'somehost';
The CREATE TABLESPACE
,
CREATE USER
, FILE
, PROCESS
, RELOAD
,
REPLICATION CLIENT
, REPLICATION SLAVE
, SHOW DATABASES
, SHUTDOWN
,
and SUPER
static privileges are administrative and can only be granted globally.
Dynamic privileges are all global and can only be granted globally.
Other privileges can be granted globally or at more specific levels.
The effect of GRANT OPTION
granted at
the global level differs for static and dynamic privileges:
GRANT OPTION
granted for any static global privilege applies to all static global privileges.GRANT OPTION
granted for any dynamic privilege applies only to that dynamic privilege.
GRANT ALL
at the global level grants all static global privileges and all currently registered dynamic privileges. A dynamic privilege registered subsequent to execution of the GRANT
statement is not granted retroactively to any account.
MySQL stores global privileges in the mysql.user
system table.
Database privileges apply to all objects in a given
database. To assign database-level privileges, use ON
syntax: db_name
.*
GRANT ALL ON mydb.* TO 'someuser'@'somehost';
GRANT SELECT, INSERT ON mydb.* TO 'someuser'@'somehost';
If you use ON *
syntax [rather than ON *.*
], privileges are assigned at the database level for the default database. An error occurs if there is no default database.
The CREATE
,
DROP
, EVENT
, GRANT OPTION
, LOCK TABLES
, and
REFERENCES
privileges can be specified at the database level. Table or routine privileges also can be specified at the database level, in which case they apply to all tables or routines in the database.
MySQL stores database privileges in the mysql.db
system table.
Table
privileges apply to all columns in a given table. To assign table-level privileges, use ON
syntax: db_name.tbl_name
GRANT ALL ON mydb.mytbl TO 'someuser'@'somehost';
GRANT SELECT, INSERT ON mydb.mytbl TO 'someuser'@'somehost';
If you specify tbl_name
rather than db_name.tbl_name
, the statement applies to tbl_name
in the default database. An error occurs if there is no default database.
The permissible priv_type
values at the table level are ALTER
,
CREATE VIEW
, CREATE
, DELETE
, DROP
,
GRANT OPTION
, INDEX
, INSERT
, REFERENCES
,
SELECT
, SHOW VIEW
, TRIGGER
, and UPDATE
.
Table-level
privileges apply to base tables and views. They do not apply to tables created with CREATE
TEMPORARY TABLE
, even if the table names match. For information about TEMPORARY
table privileges, see Section 13.1.20.2,
“CREATE TEMPORARY TABLE Statement”.
MySQL stores table privileges in the mysql.tables_priv
system table.
Column privileges apply to single columns in a given table. Each privilege to be granted at the column level must be followed by the column or columns, enclosed within parentheses.
GRANT SELECT [col1], INSERT [col1, col2] ON mydb.mytbl TO 'someuser'@'somehost';
The permissible priv_type
values for a column [that is, when you use a
column_list
clause] are INSERT
, REFERENCES
, SELECT
, and
UPDATE
.
MySQL stores column privileges in the mysql.columns_priv
system table.
The ALTER ROUTINE
,
CREATE ROUTINE
, EXECUTE
, and GRANT OPTION
privileges apply to stored routines [procedures and functions]. They can be granted at the global and database levels. Except for
CREATE ROUTINE
, these privileges can be granted at the routine level for individual routines.
GRANT CREATE ROUTINE ON mydb.* TO 'someuser'@'somehost';
GRANT EXECUTE ON PROCEDURE mydb.myproc TO 'someuser'@'somehost';
The permissible priv_type
values at the routine level are ALTER
ROUTINE
,
EXECUTE
, and GRANT OPTION
. CREATE ROUTINE
is not a routine-level privilege because you must have the privilege at the global or database level to create a routine in the
first place.
MySQL stores routine-level privileges in the mysql.procs_priv
system table.
The PROXY
privilege enables one user to be a proxy for another. The proxy user impersonates or takes the identity of the proxied user; that is, it assumes the privileges of the proxied user.
GRANT PROXY ON 'localuser'@'localhost' TO 'externaluser'@'somehost';
When PROXY
is granted, it must be the only privilege named in the GRANT
statement, and the only permitted WITH
option is WITH
GRANT OPTION
.
Proxying requires that the proxy user authenticate through a plugin that returns the name of the proxied user to the
server when the proxy user connects, and that the proxy user have the PROXY
privilege for the proxied user. For details and examples, see Section 6.2.19, “Proxy Users”.
MySQL stores proxy privileges in the mysql.proxies_priv
system table.
GRANT
syntax without an ON
clause
grants roles rather than individual privileges. A role is a named collection of privileges; see Section 6.2.10, “Using Roles”. For example:
GRANT 'role1', 'role2' TO 'user1'@'localhost', 'user2'@'localhost';
Each role to be granted must exist, as well as each user account or role to which it is to be granted. As of MySQL 8.0.16, roles cannot be granted to anonymous users.
Granting a role does not automatically cause the role to be active. For information about role activation and inactivation, see Activating Roles.
These privileges are required to grant roles:
If you have the
ROLE_ADMIN
privilege [or the deprecatedSUPER
privilege], you can grant or revoke any role to users or roles.If you were granted a role with a
GRANT
statement that includes theWITH ADMIN OPTION
clause, you become able to grant that role to other users or roles, or revoke it from other users or roles, as long as the role is active at such time as you subsequently grant or revoke it. This includes the ability to useWITH ADMIN OPTION
itself.To grant a role that has the
SYSTEM_USER
privilege, you must have theSYSTEM_USER
privilege.
It is possible to
create circular references with GRANT
. For example:
CREATE USER 'u1', 'u2';
CREATE ROLE 'r1', 'r2';
GRANT 'u1' TO 'u1'; -- simple loop: u1 => u1
GRANT 'r1' TO 'r1'; -- simple loop: r1 => r1
GRANT 'r2' TO 'u2';
GRANT 'u2' TO 'r2'; -- mixed user/role loop: u2 => r2 => u2
Circular grant references are permitted but add no new privileges or roles to the grantee because a user or role already has its privileges and roles.
TheAS
Clause and Privilege Restrictions As of MySQL 8.0.16,
GRANT
has an AS
clause that specifies additional information about the privilege context to use for statement execution. This syntax is visible at the SQL level, although its primary purpose is to enable uniform replication across all nodes of grantor privilege restrictions imposed by partial revokes, by causing those restrictions to appear in the
binary log. For information about partial revokes, see Section 6.2.12, “Privilege Restriction Using Partial Revokes”. user
[WITH ROLE]
When the AS
clause is specified, statement execution takes into account any privilege restrictions associated with the named user, including all roles specified by user
WITH ROLE
, if present. The result is
that the privileges actually granted by the statement may be reduced relative to those specified.
These conditions apply to the AS
clause: user
AS
has an effect only when the nameduser
has privilege restrictions [which implies that thepartial_revokes
system variable is enabled].If
WITH ROLE
is given, all roles named must be granted to the nameduser
.The named
user
should be a MySQL account specified as'
,user_name
'@'host_name
'CURRENT_USER
, orCURRENT_USER[]
. The current user may be named together withWITH ROLE
for the case that the executing user wantsGRANT
to execute with a set of roles applied that may differ from the roles active within the current session.AS
cannot be used to gain privileges not possessed by the user who executes theGRANT
statement. The executing user must have at least the privileges to be granted, but theAS
clause can only restrict the privileges granted, not escalate them.With respect to the privileges to be granted,
AS
cannot specify a user/role combination that has more privileges [fewer restrictions] than the user who executes theGRANT
statement. TheAS
user/role combination is permitted to have more privileges than the executing user, but only if the statement does not grant those additional privileges.AS
is supported only for granting global privileges [ON *.*
].AS
is not supported forPROXY
grants.
The following example illustrates the effect of the AS
clause. Create a user u1
that has some global privileges, as well as restrictions on those privileges:
CREATE USER u1;
GRANT SELECT, INSERT, UPDATE, DELETE ON *.* TO u1;
REVOKE INSERT, UPDATE ON schema1.* FROM u1;
REVOKE SELECT ON schema2.* FROM u1;
Also create a role r1
that lifts some of the privilege restrictions and grant the role to u1
:
CREATE ROLE r1;
GRANT INSERT ON schema1.* TO r1;
GRANT SELECT ON schema2.* TO r1;
GRANT r1 TO u1;
Now, using an account that has no privilege restrictions of its own, grant to multiple users the same set of global privileges, but each with different restrictions imposed by the AS
clause, and check which privileges are actually granted.
The
GRANT
statement here has noAS
clause, so the privileges granted are exactly those specified:mysql> CREATE USER u2; mysql> GRANT SELECT, INSERT, UPDATE ON *.* TO u2; mysql> SHOW GRANTS FOR u2; +-------------------------------------------------+ | Grants for u2@% | +-------------------------------------------------+ | GRANT SELECT, INSERT, UPDATE ON *.* TO `u2`@`%` | +-------------------------------------------------+
The
GRANT
statement here has anAS
clause, so the privileges granted are those specified but with the restrictions fromu1
applied:mysql> CREATE USER u3; mysql> GRANT SELECT, INSERT, UPDATE ON *.* TO u3 AS u1; mysql> SHOW GRANTS FOR u3; +----------------------------------------------------+ | Grants for u3@% | +----------------------------------------------------+ | GRANT SELECT, INSERT, UPDATE ON *.* TO `u3`@`%` | | REVOKE INSERT, UPDATE ON `schema1`.* FROM `u3`@`%` | | REVOKE SELECT ON `schema2`.* FROM `u3`@`%` | +----------------------------------------------------+
As mentioned previously, the
AS
clause can only add privilege restrictions; it cannot escalate privileges. Thus, althoughu1
has theDELETE
privilege, that is not included in the privileges granted because the statement does not specify grantingDELETE
.The
AS
clause for theGRANT
statement here makes the roler1
active foru1
. That role lifts some of the restrictions onu1
. Consequently, the privileges granted have some restrictions, but not so many as for the previousGRANT
statement:mysql> CREATE USER u4; mysql> GRANT SELECT, INSERT, UPDATE ON *.* TO u4 AS u1 WITH ROLE r1; mysql> SHOW GRANTS FOR u4; +-------------------------------------------------+ | Grants for u4@% | +-------------------------------------------------+ | GRANT SELECT, INSERT, UPDATE ON *.* TO `u4`@`%` | | REVOKE UPDATE ON `schema1`.* FROM `u4`@`%` | +-------------------------------------------------+
If a GRANT
statement includes an AS
clause, privilege restrictions on the user who executes the statement are ignored [rather than applied as they would be in the absence of an user
AS
clause].
The optional WITH
clause is used to enable a user to grant privileges to other users. The WITH
GRANT OPTION
clause gives the user the ability to give to other users any privileges the user has at the specified privilege level.
To grant the GRANT OPTION
privilege to an
account without otherwise changing its privileges, do this:
GRANT USAGE ON *.* TO 'someuser'@'somehost' WITH GRANT OPTION;
Be careful to whom you give the GRANT
OPTION
privilege because two users with different privileges may be able to combine privileges!
You cannot grant another user a privilege which you yourself do not have; the
GRANT OPTION
privilege enables you to assign only those privileges which you yourself possess.
Be aware that when you grant a user the GRANT OPTION
privilege at a particular privilege level, any privileges the user possesses [or may be given in the future] at that level can
also be granted by that user to other users. Suppose that you grant a user the INSERT
privilege on a database. If you then grant the SELECT
privilege on the database and specify WITH GRANT OPTION
, that user can give to other users not only the
SELECT
privilege, but also INSERT
. If you then grant the UPDATE
privilege to the user on the database, the user can grant
INSERT
, SELECT
, and UPDATE
.
For a nonadministrative user, you should not grant the
ALTER
privilege globally or for the mysql
system schema. If you do that, the user can try to subvert the privilege system by renaming tables!
For additional information about security risks associated with particular privileges, see Section 6.2.2, “Privileges Provided by MySQL”.
MySQL and Standard SQL Versions of GRANT The biggest differences between the MySQL and standard SQL versions of GRANT
are:
MySQL associates privileges with the combination of a host name and user name and not with only a user name.
Standard SQL does not have global or database-level privileges, nor does it support all the privilege types that MySQL supports.
MySQL does not support the standard SQL
UNDER
privilege.Standard SQL privileges are structured in a hierarchical manner. If you remove a user, all privileges the user has been granted are revoked. This is also true in MySQL if you use
DROP USER
. See Section 13.7.1.5, “DROP USER Statement”.In standard SQL, when you drop a table, all privileges for the table are revoked. In standard SQL, when you revoke a privilege, all privileges that were granted based on that privilege are also revoked. In MySQL, privileges can be dropped with
DROP USER
orREVOKE
statements.In MySQL, it is possible to have the
INSERT
privilege for only some of the columns in a table. In this case, you can still executeINSERT
statements on the table, provided that you insert values only for those columns for which you have theINSERT
privilege. The omitted columns are set to their implicit default values if strict SQL mode is not enabled. In strict mode, the statement is rejected if any of the omitted columns have no default value. [Standard SQL requires you to have theINSERT
privilege on all columns.] For information about strict SQL mode and implicit default values, see Section 5.1.11, “Server SQL Modes”, and Section 11.6, “Data Type Default Values”.