anchor.diff:  
   // https://docs.microsoft.com/en-us/sql/t-sql/statements/alter-role-transact-sql
   alter_db_role
  -    : ALTER ROLE role_name=id 
  -        ( (ADD|DROP) MEMBER database_principal=id 
  +    : ALTER ROLE role_name=id
  +        ( (ADD|DROP) MEMBER database_principal=id
           | WITH NAME EQUAL new_role_name=id )
  -    ; 
  +    ;
   
   // https://docs.microsoft.com/en-us/sql/t-sql/statements/create-role-transact-sql
   create_db_role
  
positive.code:     | VISIBILITY EQUAL (ON | OFF)
      | UNCHECKED DATA
      | assembly_option COMMA
      ;    
  
  network_file_share
      : network_file_start network_computer file_path
      ;
   
  network_computer
      : computer_name=id
      ;
  
negative.code:         ( (FOR|FROM) LOGIN login_name=id
          | WITHOUT LOGIN
          )?
  
          ( WITH DEFAULT_SCHEMA EQUAL schema_name=id)?
      | CREATE USER Azure_Active_Directory_principal=id
          FROM EXTERNAL PROVIDER
          ( WITH DEFAULT_SCHEMA EQUAL schema_name=id)?
      ;
  
  