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45 Cards in this Set

  • Front
  • Back

List the issues with managing data with traditional file processing systems.

Redundancy, Inconsistency, Data Isolation, Lack of Data Integrity, Lack of Atomicity, and Concurrent access issues.

What is Redundancy?

Lack of Data IntegrityInformation on a person, place, etc can appear many times.

What is Inconsistency?

For example, the student id may be assigned to two people. Or an invalid letter grade is assigned. Or invalid data type.

What is Data Isolation?

Data in one file is modified in isolation of other files. Relationships between data are not maintained.

What is Lack of Data Integrity?

Maintaining minimum and maximum values, making sure if one piece of data is related to another, that the data it is related to exists.

What is Lack of Atomicity?

If a transaction fails part way through execution, there is no way to detect this. Possibility of partial transactions.

What are Concurrent access issues?

Having multiple users access the same data may result in inconsistent data.

Define Physical Data Independence. Why is it important in a database system?

Physical Data Independence is the abstraction of the data, where a conceptual view of the data is separated from how it is physically stored. This allows the database administrator to change how the data is stored without changing how it is conceptually viewed.

List the 4 types of database users.

•Naive users–rely on interfaces to access/insert/update data.


•Sophisticated users–Can access/insert/update data with a query language


•Application programmers–create front-end programs for other to access data


•Database administrator (DBA)–responsible for back-end database management (i.e. physical data organization, creation of indexes, user authorization)

What is Schema?

The description of the database design.

What is a database?

A collection of data that is relevant to some world entity that contains interrelated data and has no irrelevant data.

What is a DBMS?

Software/language for data access and manipulation.

What is a data model?

A description of the database that includes: data, semantics, relationships, consistency constraints.

In database languages, what are definitions called and where are they stored?

They are called metadata and are stored in a dictionary (DUH!).

What are the 4 levels of DBMS?

Data storage, Storage Manager, Query Processor, and User Level.

What are the two main design goals for DBMS?

To eliminate/reduce:


1) Redundancy
2) Inconsistency

What are the design phases?

Initial: Identify entities, relationships, etc
Conceptual: Choose a model
Logical: Mapping
Normalization: Test for good design

What is ERM?

Entity-Relationship Model: high-level visual schema, represents entities & attributes, relationships, and supports specification of constraints.

What is an entity? Entity set?

Entity: An object in the real world.
Entity set/type: Set of entities of same type.

What is a relationship? Relationship set?

Relationship: Association among two or more entities.


Relationship Set: set of relationships of same type.
Entities participate in relationships.

What are constraints? Entity set constraints? Relationship set constraints?

Constraints: They define certain properties that data in a database must comply with.
Entity set constraints are keys, relationship set constraints are cardinalities, participation and keys.

Total vs Partial Participation

Total (Double Line): EVERYONE MUST PARTICIPATE!
Partial (Single Line): Participation not required.

Attribute Types (4)

1) Simple - atomic values


2) Composite - divisible into subparts


3) Multivalued (double oval) - multiple values for an entity


4) Derived (dotted oval) - from other values

Strong vs Weak Entity Set Variations

Strong - Uniquely identified


Weak - Not uniquely identified

What is a RM?

Relational Model: A collection of relations (related tables).

What are relations composed of (3)?

A relation is composed of:


1) Attributes (fields)


2) Tuples (records)


3) Constraints

How is each relation defined by?

A relation schema.

A relation populated with tuples at a given time is a...

Relation Instance

A Relation Schema:
REL(A1,A2,… An)


What does this mean?

REL is name of relation


A1, A2… An is list of attributes that describe REL

What is a domain?

A set of valid values that an attribute obtains its values from.

What are tuples?

Ordered list of values.

Name special attributes and attribute sets (4).

1) Superkey


2) Primary Key


3) Foreign Key


4) Candidate Key

What's a foreign key?

Set of attributes in a relation that references the primary key in another relation.

What are the Characteristics of Relations (4)?

1) Tuples are not ordered


2) Attributes are ordered


3) All attribute values are either atomic or null


4) A null value represents:


Unknown or Not applicable

What is the relation?

What is the relation?

E(pk,a2,a3)

What is the relation?

What is the relation?

E(pk,sa1,sa2,a3)

What is the relation?

What is the relation?

WE(pk, partkey, a2, a3)


-foreign key pk references E

What is the relation?

What is the relation?

E2(pk2,pk,a2,a3)


-foreign key pk references E1

What is the relation?

What is the relation?

R(pk, pk2)


-foreign key pk references E1,


pk2 references E2

What is the relation?

What is the relation?

E2(pk2,pk,a2,a3)


-foreign key pk references E1

What is the relation?

What is the relation?

R(pk2, pk)


-foreign key pk references E1,


pk2 references E2

What is the relation?

What is the relation?

R(pk2, pk)


-foreign key pk references E1,


pk2 references E2

What are the relations?

What are the relations?

E(pk,a2,a3)


SE1(pk,sa1)


-foreign key pk references E


SE2(pk,sa2,sa3)


-foreign key pk references E

What are the relations?

What are the relations?

SE1(pk,a2,a3,sa1)


SE2(pk,a2,a3,sa2,sa3)

What are the two Specialization Constraints and the differences between the two?

Disjoint & Overlapping. Disjoint are always partial participation.