Exercise #59 (tips and solutions) |
||
The 2.2.1 decision ignores the fact that it might happen that at some point only income may be, but outcome not to be, i.e. it is possible that Outcome_o table does not have any rows related to the this point. In terms of subject area, this situation is possible to new reception point, when the fact of cash income already recorded, but the fact of cash outcome is not. Then the expression in the SELECT clause
Correct solution is very easy by rewriting the erroneous expression in the form:
To return to discussion of exercise #59 |