Chapter 5 DAD220 SNHU UPDATED
ACTUAL Questions and CORRECT
Answers
fact - CORRECT ANSWER- related values
redundancy - CORRECT ANSWER- repetition of a fact
normal forms - CORRECT ANSWER- rules for designing tables with less redundancy
The six normal forms comprise a sequence, with each normal form allowing less redundancy
than the prior normal form.
What are the Normal Forms - CORRECT ANSWER- Normal forms are numbered, first
normal form through fifth normal form. An additional normal form, named Boyce-Codd normal
form, is considered an improved version of third normal form.
First normal form - CORRECT ANSWER- all non-key columns must depend on the primary
key
What does dependence mean in an ERD? - CORRECT ANSWER- each instance of a
dependent entity always relates to an instance of another entity
Called: Existence dependence
What does dependence mean in a relational model? - CORRECT ANSWER- each value of a
column relates to at most one value of another column
Called: Functional dependence
, second normal form - CORRECT ANSWER- all non-key columns must depend on the
whole primary key.
In other words, a non-key column cannot depend on part of a composite primary key.
Third normal form - CORRECT ANSWER- All non-key columns depend on the key, the
whole key, and nothing but the key.
In what situations is redundancy more acceptable? - CORRECT ANSWER- In a database
used primarily for reporting, changes are infrequent and redundancy is acceptable. In fact,
redundancy can be desirable in reporting databases, as processing is faster and queries are
simpler. For this reason, reporting databases may contain tables that, by design, are not in third
normal form.
Denormalization - CORRECT ANSWER- intentionally introducing redundancy by merging
tables.
Denormalization eliminates join queries and therefore improves query performance.
Aggregate Functions in SQL - CORRECT ANSWER- Used to summarize information from
multiple tuples into a single-tuple summary
Some common aggregat functions - CORRECT ANSWER- COUNT() - Counts the number
of rows retrieved by a SELECT statement.
MIN() - Finds the minimum value in a group.
MAX() - Finds the maximum value in a group.
SUM() - Sums all the values in a group.
AVG() - Finds the arithmetic mean (average) of all the values in a group.
GROUP BY clause does what? - CORRECT ANSWER- groups rows with identical values
into a set of summary rows
ACTUAL Questions and CORRECT
Answers
fact - CORRECT ANSWER- related values
redundancy - CORRECT ANSWER- repetition of a fact
normal forms - CORRECT ANSWER- rules for designing tables with less redundancy
The six normal forms comprise a sequence, with each normal form allowing less redundancy
than the prior normal form.
What are the Normal Forms - CORRECT ANSWER- Normal forms are numbered, first
normal form through fifth normal form. An additional normal form, named Boyce-Codd normal
form, is considered an improved version of third normal form.
First normal form - CORRECT ANSWER- all non-key columns must depend on the primary
key
What does dependence mean in an ERD? - CORRECT ANSWER- each instance of a
dependent entity always relates to an instance of another entity
Called: Existence dependence
What does dependence mean in a relational model? - CORRECT ANSWER- each value of a
column relates to at most one value of another column
Called: Functional dependence
, second normal form - CORRECT ANSWER- all non-key columns must depend on the
whole primary key.
In other words, a non-key column cannot depend on part of a composite primary key.
Third normal form - CORRECT ANSWER- All non-key columns depend on the key, the
whole key, and nothing but the key.
In what situations is redundancy more acceptable? - CORRECT ANSWER- In a database
used primarily for reporting, changes are infrequent and redundancy is acceptable. In fact,
redundancy can be desirable in reporting databases, as processing is faster and queries are
simpler. For this reason, reporting databases may contain tables that, by design, are not in third
normal form.
Denormalization - CORRECT ANSWER- intentionally introducing redundancy by merging
tables.
Denormalization eliminates join queries and therefore improves query performance.
Aggregate Functions in SQL - CORRECT ANSWER- Used to summarize information from
multiple tuples into a single-tuple summary
Some common aggregat functions - CORRECT ANSWER- COUNT() - Counts the number
of rows retrieved by a SELECT statement.
MIN() - Finds the minimum value in a group.
MAX() - Finds the maximum value in a group.
SUM() - Sums all the values in a group.
AVG() - Finds the arithmetic mean (average) of all the values in a group.
GROUP BY clause does what? - CORRECT ANSWER- groups rows with identical values
into a set of summary rows
