MySQL - include a default value in LOAD XML INFILE statement
When one needs to do something more complex that is available in the syntax, it is often useful to 'stage' the data through a temp table:

Perhaps:

CREATE TEMPORARY TABLE tmp ( ... DEFAULT 'myfile' ... );
LOAD XML ...;
INSERT INTO tab1 SELECT * FROM tmp;


or:

CREATE TEMPORARY TABLE tmp LIKE tab1;
LOAD XML ...;
UPDATE tmp SET DEFAULT = 'myfile';
INSERT INTO tab1 SELECT * FROM tmp;