Populating Nulls when using left join

[alan_grn]

I am trying to ginf the best way to populate a field when using a left join.

If the field in the right hand tabel is blank, it is then to be populaetd with one of the fields of the left hand table.

I can do this by reloading the table after running the join by using code such as :

Load IF(isNull(field),table1field,field) from resident table x;

I was wondering if ther is anotehr way of doing this without having to relaod the table.