Database Chapters 3 And 7

Front 1

The number of participating entities in a relationship is called its _______?

Back 1

degree

Front 2

When an entity participates with itself in different roles of a relationship this is called _____? An example is one EMPLOYEE (supervising) another EMPLOYEE

Back 2

Recursive Relationship

Front 3

In a binary relationship this specifies the maximum number of relationship instances an entity can participate in.

Back 3

Cardinality Ratios
Can be:
1) 1 to 1 (1:1)
2) 1 to many (1:M)
3) many to 1 (M:1)
4) many to many (M:N)

Front 4

These specify the minimum number of relationship instances each entity can participate in.

Back 4

Participation constraints
"miinimum cardinality constraint"

Front 5

This is when ever entity in an entity set must be related to an entity in the other entity set.
Example: WORKS_FOR – every EMPLOYEE must be related to a DEPARTMENT entity via the WORKS_FOR relationship

Back 5

Total Participation Constraint

Front 6

This is when some entities in an entity set are related to an entity in the other set but it is not required.
Example: MANAGES – only some EMPLOYEE entities are managers for DEPARTMENT entities

Back 6

Partial Participation Constraint

Front 7

Total Participation constraints are indicated by what?

Back 7

Double lines

Front 8

(Relationship attributes) for 1:1 relationships the attributes can be _____?

Back 8

on either side

Front 9

(Relationship attributes) For 1:N relationships the attributes can be ____?

Back 9

Only on side of the "many entity" side

Front 10

(Relationship attributes) For M:N relationships the attributes are determined by a combination of both entities. These cannot be modeled as part of entity type but rather _____?

Back 10

as part of relationship type

Front 11

These are entity types without a key attibute. They are considered to belong to another entity in another set, called the identifying entity type.

Back 11

Weak Entity Types

Front 12

In a relational model this is one row of a relation.

Back 12

Tuple

Front 13

in a relational model this is one column of a relation.

Back 13

Attribute

Front 14

in a relational model this is the who table.

Back 14

Relation

Front 15

In a relational model this is all the values that attributes can have.

Back 15

Domain of an Attribute

Front 16

This is all the possible values an attribute can take in a relational model. It is atomic and has a specific data type.

Back 16

Domain

Front 17

In a relational model this consists of a relation name and a list of attributes. It is a description of what the relation should contain and is denoted by R(A1, A2, ....An). Example: STUDENT(Name, SSN, Address, GPA)

Back 17

Relation Schema

Front 18

This is the number of attributes n of its relation schema.

Back 18

Degree (or arity)

Front 19

How do you reresent Multivalued attributes in a Relational Model?

Back 19

Must be represented by seperate relations

Front 20

How do you represent Composite attributes in a Relational Model?

Back 20

Represented by simple component ttributes in a basic Relational Model

Front 21

(Schema-based constraints) What are the 2 key aspects of Domain constraints?

Back 21

1) Data type constraint
2) Each attibute may only take on a value from the domain of that attribute

Front 22

(Schema-based constraints) what are the 2 key aspects of key constraints?

Back 22

1) Each tuple in a relation must be unique
2) Usually there is a subset of attributes that control uniqueness- this is called a "superkey"

Front 23

What does it mean to say that Superkeys can have redundant attributes?

Back 23

Example {First_Name, Last_Name, SSN) can be a Superkey but you don't need First_Name and Last_Name as SSN is guaranteed to be unique.

Front 24

This is a minimal Superkey. AKA you remove one attribute and it is no longer a superkey.

Back 24

key (note all keys are superkeys but not all superkeys are keys.)

Front 25

(Schema-based constraints) Set of relation schemas S = {R1, R2,.... Rm}

Back 25

Relational Database Schema

Front 26

(Schema-based constraints) Set of relation states for a relational database such that all integrity constraints are satisfied.

Back 26

Relation Database State

Front 27

(Schema-based constraints) No primary key can have a NULL value

Back 27

Entity integrity constraint

Front 28

(Schema-based constraints) Specified between two relations. A tuple in one relation that refers to a tuple in a second relation MUST refer to an existing tuble. Uses the concept of a foreign key.

Back 28

Referential Integrity constraint

Front 29

Informally, a value in a tuple that points to a primary key in a different tuple.

Back 29

Foreign key

Front 30

(Schema-based constraints) These constraints come from outside the basic relationships between tuples. Usually modeled at the application level, but sometimes can be modeled in the database.

Back 30

Semantic Integrity constraints

Front 31

What are the two types of operations that a relational model has?

Back 31

1) Retrievals (getting info from db)
2) Updates (adding/changing info in db. Includes: insert, delete, and update)

Front 32

For Binary 1:1 Relationships If two entities have TOTAL participation in a relationship, then you can turn them into a single entity.

Back 32

Merged Relation Approach

Front 33

For Binary 1:1 Relationships Set up a third relation as a lookup table for the relationship.

Back 33

Cross-referenced approach (required for M:N relations)

Front 34

For binary 1:N relationships you should use this approach. It identifies which relation represents the entity on "many" side of the relationship. Points to primary key on the "one" side of relationship

Back 34

Foreign Key approach (can also be used for 1:1)

Front 35

For Binary M:N Relationships you should use this approach. For Entities E1 and E2 connected by Relationship R, create a rew relation for R. It will include, as attributes, foreign keys pointing at primary keys of E1 and E2 combining into a primary key.

Back 35

Cross-reference approach. You also include any attributes tied to R

Front 36

What do you do for multivalued attributes on in ER to Relation model mapping?

Back 36

Create new relation taht has a foreign key pointing at the primary key of initial relation.

Front 37

For N-ary Relationships you should use this approach?

Back 37

Cross-reference approach.