Certain Answers

Question 1

In a Codd table, all NULLs are replaced with ________

Answer 1

variables/constants

Question 2

An incomplete database is a set of _____ tables

Answer 2

Codd

Question 3

An incomplete database represents infinitely many ______ _____

Answer 3

possible worlds

Question 4

A possible world is obtained by replacing ______ with actual values

Answer 4

NULLs

Question 5

A certain answer always gives the same results _________ of how we instantiate the NULLs

Answer 5

independent

Question 6

In naive implementation of querying incomplete DBs, we treat the variables/NULLs as _______

Answer 6

constants

Question 7

In naive implementation of querying incomplete DBs, problems arise with ______

Answer 7

negation

Question 8

SQL does not use ______ evaluation in comparisons

Answer 8

naive

Question 9

You can never trust the answers you get from a database with _____

Answer 9

NULLS

Question 10

When talking about correctness in SQL, what does Q+ and Q? represent?

Answer 10

Q+ approximates certain answers

Q? represents possible answers

Question 11

cert(Q,D) is a subset of ___ and is a superset of ___

Answer 11

Q?, Q+

Question 12

REVIEW CORRECTNESS IN SQL: TRANSLATION SLIDE

Answer 12

REVIEW CORRECTNESS IN SQL: TRANSLATION SLIDE

Question 13

The way SQL handles incomplete data is _______, ________, and _____

Answer 13

ambiguous, inconsistent, incorrect