MySQL account names consist of a user name and a host name. This enables creation of accounts for users with the same name who can connect from different hosts. This section describes how to write account names, including special values and wildcard rules.
In SQL statements such as CREATE
USER, GRANT, and
SET PASSWORD, write account names
using the following rules:
Syntax for account names is
'.user_name'@'host_name'An account name consisting only of a user name is equivalent to
'. For example,user_name'@'%''me'is equivalent to'me'@'%'.The user name and host name need not be quoted if they are legal as unquoted identifiers. Quotes are necessary to specify a
user_namestring containing special characters (such as “-”), or ahost_namestring containing special characters or wildcard characters (such as “%”); for example,'test-user'@'%.com'.Quote user names and host names as identifiers or as strings, using either backticks (“
`”), single quotation marks (“'”), or double quotation marks (“"”).The user name and host name parts, if quoted, must be quoted separately. That is, write
'me'@'localhost', not'me@localhost'; the latter is interpreted as'me@localhost'@'%'.A reference to the
CURRENT_USER()(orCURRENT_USER) function is equivalent to specifying the current user's name and host name literally.
MySQL stores account names in grant tables in the
mysql database using separate columns for the
user name and host name parts:
The
usertable contains one row for each account. TheUserandHostcolumns store the user name and host name. This table also indicates which global privileges the account has.Other grant tables indicate privileges an account has for databases and objects within databases. These tables have
UserandHostcolumns to store the account name. Each row in these tables associates with the account in theusertable that has the sameUserandHostvalues.
For additional detail about grant table structure, see Section 5.4.2, “Privilege System Grant Tables”.
User names and host names have certain special values or wildcard conventions, as described following.
A user name is either a nonblank value that literally matches the
user name for incoming connection attempts, or a blank value
(empty string) that matches any user name. An account with a blank
user name is an anonymous user. To specify an anonymous user in
SQL statements, use a quoted empty user name part, such as
''@'localhost'.
The host name part of an account name can take many forms, and wildcards are permitted:
A host value can be a host name or an IP address. The name
'localhost'indicates the local host. The IP address'127.0.0.1'indicates the loopback interface. For the local host, the host value can be the IPv6 address'::1', which indicates the IPv6 loopback interface.You can use the wildcard characters “
%” and “_” in host values. These have the same meaning as for pattern-matching operations performed with theLIKEoperator. For example, a host value of'%'matches any host name, whereas a value of'%.mysql.com'matches any host in themysql.comdomain.'192.168.1.%'matches any host in the 192.168.1 class C network.Because you can use IP wildcard values in host values (for example,
'192.168.1.%'to match every host on a subnet), someone could try to exploit this capability by naming a host192.168.1.somewhere.com. To foil such attempts, MySQL disallows matching on host names that start with digits and a dot. Thus, if you have a host named something like1.2.example.com, its name never matches the host part of account names. An IP wildcard value can match only IP addresses, not host names.For a host value specified as an IP address, you can specify a netmask indicating how many address bits to use for the network number. The syntax is
host_ip/netmaskCREATE USER 'david'@'192.58.197.0/255.255.255.0';
This enables
davidto connect from any client host having an IP addressclient_ipfor which the following condition is true:client_ip&netmask=host_ipThat is, for the
CREATE USERstatement just shown:client_ip& 255.255.255.0 = 192.58.197.0IP addresses that satisfy this condition and can connect to the MySQL server are those in the range from
192.58.197.0to192.58.197.255.The netmask can only be used to tell the server to use 8, 16, 24, or 32 bits of the address. Examples:
192.0.0.0/255.0.0.0: Any host on the 192 class A network192.168.0.0/255.255.0.0: Any host on the 192.168 class B network192.168.1.0/255.255.255.0: Any host on the 192.168.1 class C network192.168.1.1: Only the host with this specific IP address
The following netmask will not work because it masks 28 bits, and 28 is not a multiple of 8:
192.168.0.1/255.255.255.240