Depending on how many rows are in your table, you can do it manually or with
a cursor. -----> What do you mean by doing it manually or with cursor?

UPDATE <table name>
SET
<field1> = ' ', --there's a space between the two single quote marks
<field2> = ' ', --in both these lines
WHERE <shouldn't be null field> IS NULL

The problem is what if in record 1 the field that has a NULL value is
Field2, then the next record, record 2, the field that has a NULL value is
Field5 and so on on so forth.  Will the statement you give solve this
problem?  Sorry I'm just new to update statement and I have only used it for
a single updates.

Thanks,

Enzo