database midterm

Question 1

purpose of a database

Answer 1

to store data

Question 2

instance in a database

Answer 2

is a single occurrence within that table eg. a row in the student table

Question 3

attribute

Answer 3

is each column in the table

Question 4

microsoft access is a what?

Answer 4

Good database for beginners but not for professionals

Question 5

what is the dominant database model

Answer 5

relational database model

Question 6

SQL

Answer 6

structured query language was developed by IBM in the 70’s. Not a full program language it is a sublanguage.

Question 7

2 categories of SQL

Answer 7

data definition language and data manipulation language.

Question 8

Data definition language:

Answer 8

statemns used for creating tables, relationships and other structures

Question 9

Data manipulaion language

Answer 9

statements used for reading writing deleting and updating records

Question 10

SQL select statement

Answer 10

select columnName
from: TableName
Where: conditions

Question 11

How do you select all columns in table

Answer 11

asterisk in the select part

Question 12

Entity

Answer 12

is some identifiable thing that users want to track: Students, factulty, courses, schools

Question 13

functional dependency

Answer 13

ocurs when the value of one attribute determines the value of a second attribute

EX: StudentId is a determinant of name

Question 14

composite determinant

Answer 14

a determinant of a functional dependency that consists of more than one attribute

Question 15

Unique determinant:

Answer 15

is only when it determines every other column in the relation.

Question 16

Candidate key:

Answer 16

is a key that determines all of the other columns in a relation. from the candidate keys one will be the primary key.

Question 17

primary key

Answer 17

is a candidate key that is selected to uniquely identify a row in a relation. must be unique

Question 18

Surrogate Key

Answer 18

is an artificial column added to a relation to serve as a primary key. this is done with a good PK cannot be found.

Question 19

foreign key

Answer 19

is the primary key of one relation that is placed in another relation to form a link between the relations. the foreign key of one table must be a PK in another table

Question 20

Referential integrity constraint

Answer 20

limts the foreign key to be a PK in another table

Question 21

multi-valued dependency

Answer 21

occurs when a determinant is matched with a particular set of values

Question 22

how do you count the number of rows in a table

Answer 22

COUNT (*)

Question 23

when does it not matter if they database is in BCNF or not

Answer 23

if it is a updateable database or not

Question 24

how do you copy info to another table?

Answer 24

use the command insert into tableName

Question 25

Read-only databases:

Answer 25

are nonoperational databases using data extracted from operational databases. used for querying reporting and data mining applications they are never updated.

Question 26

denormalization

Answer 26

is the joining of the data in normalized tables prior to storing the data.

Question 27

multivalue, multicolumn problem

Answer 27

occurs when multiple values of an attribute are stored in more than one column. solution to this is to use a separate table to store the multiple values

Question 28

inconsistent values

Answer 28

occur when different users or different data sources use slightly different forms of the same data value

Question 29

missing values or null value:

Answer 29

is a value that has never been provided

Question 30

general purpose remarks column

Answer 30

is a column with a name such as remaks comments or notes. it often contains important data stored in an inconsistant verbal way.

Question 31

Data model

Answer 31

is a plan or blueprint for a database design

Question 32

entity relationship model

Answer 32

is a set of concepts and graphical symbols that can be used to create conceptual schemas

Question 33

attributes:

Answer 33

describe an entity’s characteristics. all entity instances of a gien entity class have the same attributes but vary in the value of those attributes.

Question 34

identifiers

Answer 34

are attributes that name or identify entity instances.

Question 35

cardinality

Answer 35

means count as is expressed as a number it is the number of entity instances that can participate in a relationship. I.E. maximum and minimum cardinality

Question 36

maximum cardinality

Answer 36

one-one, one-many, many-many

Question 37

minimum cardinality

Answer 37

is the minimum number of entity instances that must participate in a relatioship. usually stated as 0 or 1

Question 38

SQL

Answer 38

is internationaly recongnized standard database language that is used by all commercial dbms’s

Question 39

composite identifiers

Answer 39

are identifiers that consist of two or more attributes.