MySQL Permissions – Grant Read-Only Access for One DB and Create/Drop Access for Others

If you have a list of known usernames, you can store them in a table somewhere:

CREATE TABLE dbo.WebDevelopers(name SYSNAME PRIMARY KEY);

INSERT dbo.WebDevelopers(name)
  SELECT N'YourDomain\User1'
  UNION ALL 
  SELECT N'YourDomain\User2';

Now you can create a variety of scripts to ensure that:

1. they exist as a login at the server level

2. for each relevant database:

   • they exist as a user
   • they are in the db_datareader role
   • they have SELECT permission on the dbo schema

Here is a start to solve 1. (I'll come back and address the others as I have time later today):

DECLARE @sql NVARCHAR(MAX), @cr NCHAR(2) = CHAR(13) + CHAR(10);

SELECT @sql = N'';

SELECT @sql = @sql + @cr + 'CREATE LOGIN '
 + QUOTENAME(d.name) + ' FROM WINDOWS;'
FROM dbo.WebDevelopers AS d
LEFT OUTER JOIN sys.server_principals AS p
ON d.name = p.name
WHERE p.name IS NULL;

PRINT @sql;
-- EXEC sp_executesql @sql;

For the rest, this makes some basic assumptions: you always elevate privileges using database-level roles, rather than explicit GRANT/DENY, server role membership or AD group membership. Like the table of developers, you also want to have somewhere a list of the databases you want to affect:

CREATE TABLE dbo.DeveloperDatabases(name SYSNAME PRIMARY KEY);

INSERT dbo.DeveloperDatabases(name)
  SELECT N'some_database'
  -- UNION ALL N'...';

Now you can build a script that will drop the user from each database, create the entire list from scratch, and add each user only to the db_datareader role. You may want to customize the script if you want to grant explicit rights on a certain schema or set of objects.

DECLARE @sql NVARCHAR(MAX), @cr NCHAR(2) = CHAR(13) + CHAR(10);

SELECT @sql = N'SELECT @sql2 = N'''';';

SELECT @sql = @sql + @cr + N'SELECT @sql2 = @sql2 + ''
  USE ' + QUOTENAME(name) + '; 
  DROP USER '' + QUOTENAME(d.name) + '';''
FROM dbo.WebDevelopers AS d
INNER JOIN ' + QUOTENAME(name) + '.sys.database_principals AS p
ON d.name = p.name;'
FROM dbo.DeveloperDatabases;

SELECT @sql = @sql + @cr + N'SELECT @sql2 = @sql2 + ''
  USE ' + QUOTENAME(name) + '; 
  CREATE USER '' + QUOTENAME(d.name) + '' FROM LOGIN '' + QUOTENAME(d.name) + '';
  EXEC sp_addrolemember ''''db_datareader'''', '''''' + d.name + '''''';''
FROM dbo.WebDevelopers AS d
LEFT OUTER JOIN ' + QUOTENAME(name) + '.sys.database_principals AS p
ON d.name = p.name
WHERE p.name IS NULL;'
FROM dbo.DeveloperDatabases;

DECLARE @sql2 NVARCHAR(MAX);

EXEC sp_executesql @sql, N'@sql2 NVARCHAR(MAX) OUTPUT', @sql2 OUTPUT;

PRINT @sql2;
-- EXEC sp_executesql @sql2;

This is very rough, and lots of things can make it break. I could have combined the two selects into a single query but I think double-nested dynamic SQL was complex enough without adding conditional string concatenation in there as well.

As the error message itself says that user do not have the execute permissions.

mysql> SELECT hello('world');
ERROR 1370 (42000): execute command denied to user ''@'localhost' for routine 'test.hello'

You need to grant the Execute Permission to that user.For that you need to login as root user and grant the permission as

 grant execute on db.* to user@localhost;

For your other queries :

1. Yes It is possible that your username is an empty string but it is not safe to create the users like this.

2. For creating and granting privileges in brief have a look at This Link.

3. Yes you can grant all the privileges on all entities within a database. for this you can execute a command like

Login as root user and issue a command

GRANT ALL ON DB_NAME.* TO 'USER'@'HOST' IDENTIFIED BY 'PASSWORD' WITH GRANT OPTION;