i try a mapping with a lookup table to update a column.
update table1 x
set x.col1 = (select y.col2 from table2 y
where trim(x.a_old) = trim(y.a_new)
and trim(x.b_old) = trim(y.b_new)
where x.col1 is null;
unfortunately the columns x.b_old and y.b_new can be null and then i get no match.
why can i not match trim(null) = trim(null)? is there a solution? I could use a case but that would lower performance.