如何通用/动态创建/删除用户

(与…有关,但与…分开 Syntax error with emulating "create user if not exists" 。)

是否可以实现一般/动态添加用户的功能(即模拟 sp_adduser mysql中是否包含其他dbms的系统过程?

MySQL不支持以下内容 if [not] exists 语法,参见 http://bugs.mysql.com/bug.php?id=15287 :

create user if not exists 'foo'@'%' identified by password 'bar';

它也不支持:

drop procedure if exists create_user_if_not_exists;

delimiter ||

create procedure create_user_if_not_exists
               ( sUser     varchar(60),
                 sHost     varchar(16),
                 sPassword varchar(255) )
begin

-- ensure user does not yet exist
if (select ifnull((select 1
                     from mysql.user
                    where User = sUser
                      and Host = sHost), 0) = 0) then
  set @createUserText = concat('create user ''', sUser, '''@''', sHost, ''' identified by ''', sPassword, ''';');

  prepare createUserStatement FROM @createUserText;
  execute createUserStatement;
  deallocate prepare createUserStatement;
end if;

end ||

delimiter ;

因为如果你试图调用上述过程:

call create_user_if_not_exists ( 'foo', '%', 'bar' );

你得到了可爱的信息:

This command is not supported in the prepared statement protocol yet

以下是可行的,但显然不是特别可重用的:

drop procedure if exists create_user_if_not_exists;

delimiter ||

create procedure create_user_if_not_exists
               (  )
begin

if (select ifnull((select 1
                     from mysql.user
                    where User = 'foo'
                      and Host = '%'), 0) = 0) then
  create user 'foo'@'%' identified by password 'bar';
end if;

end ||

delimiter ;