database final

Question 1

entity is what

Answer 1

is some identifiable thing that users want to track

Question 2

functional dependency

Answer 2

occurs when the value of one set of attributes determines the value of a second set of attributes

Question 3

what is an example of functional dependency

Answer 3

studentID is a determinent of studentName

Question 4

composite determinant

Answer 4

a determinant of a functional dependency that consists of more than one attribute for example student name and class name to determine grade

Question 5

compostie key

Answer 5

is a key that consists of two or more columns

Question 6

candidate key

Answer 6

is a key that determines all of the other columns in a relation from the candidate keys the designer selects one to be the PK

Question 7

primary key

Answer 7

is a candidate key selected as the primary means of uniquely identifying a row in a relation

Question 8

Surrogate Key

Answer 8

is an artificial column added to the relation to serve as the primary key this is created when a good PK cannot be found.

Question 9

foreign key

Answer 9

is the primary key of one relation that is placed in another relation to for a link between the relations.

Question 10

referential integrity constraints

Answer 10

is a statement that limits the values of the foreign key to those already existing as primary key values in the corresponding relation.

Question 11

what is BSNF

Answer 11

boy scott normal form this is how every database should be performed

Question 12

select statement

Answer 12

select
from
where
;

Question 13

• in sql

Answer 13

means to select all columns

Question 14

sql built in functions

Answer 14

count, sum, avg, min, max

Question 15

quering multiple tables

Answer 15

must use joints by stateing the table and its fk = to table the the pk

Question 16

how do you create a table in sql

Answer 16

use create table statement but dont specify any of the FK’s untill all tables have been created and the data has been input also makeing fk’s null makes life easier

Question 17

alter table

Answer 17

used when inputing new column or fk’s

Question 18

insert command

Answer 18

used to insert values into a table

Question 19

update command

Answer 19

is used most often when you want to update an entry

Question 20

data model

Answer 20

is a plan or blueprint for a database design

Question 21

entity-relationship model

Answer 21

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

Question 22

what is and entity is a relationship model

Answer 22

this is a thing in which you want to store data like students, or employee, or courses

Question 23

an attribute in entity relationship model

Answer 23

is what describes and entity characteristics these are the columns in the table

Question 24

identifiers

Answer 24

are attributes that name or identify entity instances or the primary key these can be composite where it consists of 2 or more attributes

Question 25

binary relationship

Answer 25

is a relationship that is between 2 enteties

Question 26

a ternary relationship

Answer 26

is a relationship that is between 3 enteties

Question 27

maximum cardinality

Answer 27

is the max number of entity instances that can participate in a relationship

Question 28

minimum cardinality

Answer 28

is the minimum number of entity instances that must participatein a relationship

Question 29

what are the types of max cardinality

Answer 29

one to one, one to many, many to many

Question 30

what is the parent entity

Answer 30

this is the entity that is one the one side of the relationship

Question 31

what is the child entity

Answer 31

this is the entity on the many side of the relastionship

Question 32

minimum cardinality

Answer 32

is the minimum number of entity instances that must participate in a relationship this must be ether zero or 1

Question 33

strong entity

Answer 33

is one that represents something that can exist on its own. for example department and employee represented by a dashed line.

Question 34

weak entity

Answer 34

is one whose existance depends on the presence of another entity

Question 35

ID-dependent entity

Answer 35

is an entity whose identifier includes the identifier of another entity. the minimum cardinality for this is always one. all id dependent entities are considered weak entities.

Question 36

supertype entity

Answer 36

contains all common attributes for example the super type might be patient

Question 37

the subtype entity

Answer 37

contains specific attributes also may have a discriminator attribute which indicates the subtype the sub type would be male or female and the discriminator is sex

Question 38

exclusive subtype

Answer 38

means that the supertype can at most relate to one subtype

Question 39

an inclusive subtype

Answer 39

means at most the supertype can relate to one or more subtypes.

Question 40

a recursive relationship

Answer 40

is when the entity has a relationship to itself

Question 41

1st step in creating data mode

Answer 41

create a table for each entity, specify the PK, the candidate keys, and the properties of each column i.e. null data type

Question 42

second set in creating data model

Answer 42

create relationships by placing foreign keys, relastionships between sstrong entities, identifying relationships with ID-denpendencies , and relationships between strong and weak entities

Question 43

step 3 in creating data model

Answer 43

specify logic for enforcing minimum cardinality i.e. many to many , one to one, or one to many

Question 44

DBA's tasks

Answer 44

manage database structure, control concurrent processing, manage processing rights and responsibilities, develop database recovery, manage DBMS maintain the data repository

Question 45

a transaction

Answer 45

is a series of actions taken agains the database that occurs as an atomic unit. either all occur or none of them do.

Question 46

concurrent transaction

Answer 46

refers to two or more transactions that are being processed against a database at the same time

Question 47

implicit locks

Answer 47

are locks placed by the DBMS

Question 48

explicit locks

Answer 48

are issued by the application program

Question 49

exclusive lock

Answer 49

prohibits other users from reading the locked resource

Question 50

shared lock

Answer 50

allows other users to read the locked resource but they cannot update it

Question 51

deadlock

Answer 51

occurs when transactions are each waiting on a resource that the other transaction holds.

Question 52

preventing dead locks

Answer 52

allow users to issue all lock requests at one time repuire all application programs to lock resources inn the same order.

Question 53

breaking deadlocks

Answer 53

almost every dbms has algorithms for etecting deadlock when deadlock occurs dbms aborts one of the transactions and rollbacks partialy completed work