Ch 10

Question 1

What is a relational schema?

Answer 1

The computer’s view of the data

Question 2

In a relational data model, what corresponds with column headings, data in columns, and rows?

Answer 2

attributes, attribute values, and entities

Question 3

Every relation schema requires at least one key for the relation. – if true, relation exhibits what?

Answer 3

entity integrity

Question 4

What is a dashed circle attribute?

Answer 4

derived attribute

Question 5

For strong entity classes, what is the key of the it’s relational schema?

Answer 5

the primary key of the entity class

Question 6

What is a double circled attribute?

Answer 6

multivalued attribute

Question 7

For weak entity classes, what is the key of relation schema if

1: 1?
1: M?

Answer 7

key of owner class
key of owner class + discriminator

Question 8

For 1:1 relationship types, which class should be the recipient vs donor of foreign key?

Answer 8

the class with mandatory participation is the recipient

Question 9

Why is it a bad idea to combine two tables into one?

Answer 9

nulls may result and artificial entity means a loss of meaning and clarity

Question 10

What is a Data Dictionary?

Answer 10

single document which specifies relational schema plus all additional information

Question 11

What are the 3 goals in developing a relational schema?

Answer 11

1) each attribute and schema has a simple meaning
2) null values are minimized
3) controlled redundancy

Question 12

What is anomalous behavior?

Answer 12

change to one row of table cause problems somewhere else (where info should be the same)

Question 13

What is functional dependency?

Answer 13

a strong connection between two or more attributes in a table

Question 14

What are types of 1:1 relationships

Answer 14

"Is A" 
"Scare Resource Allocation"
"Boss"
"Marriage"
"Matching reservations"

Question 15

what steps are involved in initially creating a database?

Answer 15

Data Dictionary and relational schema diagram (normalized)

Question 16

What’s another name for entity integrity?

Answer 16

referential integrity. It ensures that you are creating a relationship between two entities

Question 17

What is the first table to populate in a database?

Answer 17

the table with no foreign keys

Question 18

when is it advantageous to split database?

Answer 18

when there are multiple users so each can have separate front end to access same data and when data from other databases needed as linked tables can come from any database.

Question 19

What are the different query operations?

Answer 19

project - take one or more columns of original table
select - take one or more rows of original table
join - combine all columns of input tables (tables must have one field in common, directly related)
set - rows come from one or other of input tables

Question 20

What is it called to join operations via a single table?

Answer 20

self join

Question 21

What does a form allow you to do?

Answer 21

view one record at a time and mix and match fields from tables and queries so that you can enter/update dat