Links to the relevant SWC teaching materials for questions:
MCQ1
If your table Visited looks like:
ident site dated
751 DR-3 1930-02-26
752 DR-3 -null-
837 MSK- 1932-01-14
Then a SQL query of
SELECT * FROM Visited WHERE dated!=NULL;
will result in the following ouput:
(1)
751 DR-3 1930-02-26
752 DR-3 -null-
837 MSK- 1932-01-14 ***
(2)
0 *** (3)
There will be no output, i.e. nothing. *** (4)
751 DR-3 1930-02-26
837 MSK- 1932-01-14 *** ***
MCQ2
In the context of programming, a precondition is:
- something that must be true at the start of a function in order for it to work correctly
- something that is always true at a particular point inside a piece of code
- a condition that must be fulfilled before other things can happen or be done
- knowing beforehand what output you would like your program to produce
This is a theoretical question, where the distractors are
- the definition of an invariant (2) (which is another concept introduced in the same module as a precondition)
- the “non-programming” definition of a precondition (3) and
- a much simpler worded statement that makes sense in the context of programming (4) (and is a precondition for you writing a program) - but is not the definition of a precondition as applied to programming or a function.