Update One Table From Another Without Join Statement

I'd like to update the columns in on table based on the values of another table, I use a slightly old version of Firebird 2.1, so it doesn't have support for the join statement dur

Solution 1:

Instead of trying to use UPDATE, use MERGE:

mergeinto elements E
  using node N
  on N.XI = E.X_I and N.YI = E.Y_I and N.ZI = E.Z_I
  when matched thenupdateset E.END_I = N.node_num

Merge allows you to use another table, view or query as source of the data to update or insert into a table.

Solution 2:

Update your query as follows

update elements E set E.END_I = (selectfirst1 n.node_num from nodes N 
where (N.XI =E.X_I and N.YI = E.Y_I and N.ZI=E.Z_I) )
whereexists (select1from nodes N where (N.XI =E.X_I and N.YI = E.Y_I and N.ZI=E.Z_I))

You should add first 1 because of Firebird 2.1 doesn't know that subquery returns only one row.