When installing the mergeusers plugin, it throws an error. Found a missing type in ./lib/dml/sqlsrv_native_moodle_database.php. Solved it by adding a line on line 715 with type CHAR, resulting in the stanza reading as follows:

          case 'CHAR':
          case 'VARCHAR':
          case 'NVARCHAR':
           $type = 'C';
           break;