You do not have permission to add users to the db_ddladmin role in the master database.
The Server admin and Azure AD admin accounts have the following characteristics:
Do not enter the master database as the dbo user, and have limited
permissions in master.
Are not members of the standard SQL Server sysadmin fixed server role,
which is not available in SQL database.
Can create, alter, and drop databases, logins, users in master, and server-level IP firewall rules.
When querying the sys.database_role_members system view in the master database, you will also see that only dbo is part of the db_owner role. For most or all other roles, no members show up.
db_accessadmin No members
db_backupoperator No members
db_datareader No members
db_datawriter No members
db_ddladmin No members
db_denydatareader No members
db_denydatawriter No members
db_securityadmin No members
dbmanager No members
loginmanager No members
public No members
This means that specific permissions are granted to the user connecting to the master database, adding users to the
db_ddladmin role in master is not one of them.
As documented, you can add users to the
loginmanager db roles in master.
alter role [dbmanager] add member sqlloginname;
alter role [loginmanager] add member sqlloginname;
You can add users to the
db_ddladmin role in user databases when connecting with the server admin since you will have dbo permissions there.
Remember that these are database roles, and that you will have to add the user per database.