Module $14$

$14\mathrm{.}1.$ Discuss attribute semantics as an informal measure of goodness for a relation schema.

$14\mathrm{.}2.$ Discuss insertion, deletion, and modification anomalies. Why are they considered bad? Illustrate with examples.

$14\mathrm{.}3.$ Why should NULLs in a relation be avoided as much as possible? Discuss the problem of spurious tuples and how we may prevent it$.$

$14\mathrm{.}4.$ State the informal guidelines for relation schema design that we discussed. Illustrate how violation of these guidelines may be harmful.

$14\mathrm{.}5.$ What is a functional dependency? What are the possible sources of the information that defines the functional dependencies that hold among the attributes of a relation schema?

$14\mathrm{.}6.$ Why can we not infer a functional dependency automatically from a particular relation state?

$14\mathrm{.}7.$ What does the term unnormalized relation refer to$?$ How did the normal forms develop historically from first normal form up to Boyce$-$Codd normal form?

$14\mathrm{.}8.$ Define first, second, and third normal forms when only primary keys are considered. How do the general definitions of $2$NF and $3$NF$,$ which consider all keys of a relation, differ from those that consider only primary keys?

$14\mathrm{.}9.$ What undesirable dependencies are avoided when a relation is in $2$NF$?$

$14\mathrm{.}10.$ What undesirable dependencies are avoided when a relation is in $3$NF$?$

$14\mathrm{.}11.$ In what way do the generalized definitions of $2$NF and $3$NF extend the definitions beyond primary keys?

$14\mathrm{.}12.$ Define Boyce$-$Codd normal form. How does it differ from $3$NF$?$ Why is it considered a stronger form of $3$NF$?$

$14\mathrm{.}13.$ What is multivalued dependency? When does it arise?