Chapter 8

Question 1

what defines a bad schema?

Answer 1

when there is a possibility of repetitions and there may be a need for null values

Question 2

why do we decompose?

Answer 2

so we can get to smaller, better schemas that have no repetition of information and no need to use null values

Question 3

what is a lossy decomposition?

Answer 3

decompose in which we lose information

Question 4

what is a decomposition that does not result in loss of info

Answer 4

lossless join decomposition

Question 5

define decomposition theory

Answer 5

decide whether particular relation R is in good form; how to decompose so that each relation is in good form, lossless join decomposition

dependent on functional dependencies and multivalued dependencies

Question 6

define functional dependencies

Answer 6

functional dependency is when a –> B

Question 7

when does a relation satisfy F

Answer 7

if relation r is legal under a set F of functional dependencies

Question 8

what does holds on mean?

Answer 8

we say that F holds on R if all legal relations on R satisfy the set of functional dependencies F

Question 9

define dependency preserving

Answer 9

sufficient to test only those depedencies on each individual relation of a decomposition in order to ensure that all functional dependencies hold