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IT 378 - Database Processing > Test 1 Study Guide > Flashcards

Test 1 Study Guide Flashcards

1
Q

What does DBMS stand for?

A

Database management system

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2
Q

What are the functions of a database management system?

A

A database management system manages the database structure, controls access to the data, and guarantees data integrity & consistency.

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3
Q

What’s the different between data and information?

A

Data is raw facts, information is the result of processing those facts to produce meaning.

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4
Q

What is a database?

A

A database is a shared, integrated computer structure that stores a collection of data and metadata.

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5
Q

What is metadata?

A

Data about data (file size, creation date, etc)

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6
Q

In what ways can a database be classified?

A

A database can be classified by the number of users it supports (one at a time or multiple), by its location (centralized vs. decentralized), and by use (operational, keeping transactions, or informational, keeping data used to generate information).

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7
Q

What is a manual file system?

A

A manual file system is literally physical files, kept in some sort of cabinet. The precursor to the database.These were eventually converted into computer systems, and functioned very similarly to the physical system, requiring data processors, and often being “home-grown”.

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8
Q

As the number of databases increased in the beginning, what changes occurred.

A

Small file systems began to evolve. Files began being used by their own application programs, and each file was owned by someone. New data processors begin being trained and hired, new programmers were brought on, data processing departments formed, although they primarily programmed.

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9
Q

Once data processing departments starting springing up, what else happened?

A

People began narrowing in on issues like data redundancy (conflicting data, etc), and system administration became complicated and difficult as systems blossomed out of control.

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10
Q

What is data-program dependence?

A

Data-program dependence is when the information of a file is dependent on the structure, which is tied directly to how the program that uses it is built. When one is changed, the others must be changed as well.

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11
Q

What are the main parts of a database system?

A

Hardware, software (OS, DBMS, Apps), People, Procedures (rules), & Data

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12
Q

What are the limitations of a file system?

A

They require extensive programming
System admin is complex and difficult
Making changes to existing structures is difficult
Security features are generally shit
Independent files usually create redundant data

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13
Q

What is a data model?

A

A data model is an abstraction of a real-world object or event. They are relatively simple representations, generally graphical.

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14
Q

What is the importance of data models?

A

Data models act as a bridge between the designer, programmer and end user, unifying their various visions of the system, combining their data needs, and improving the overall understanding of the organization.

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15
Q

What are the basic elements of a data model?

A

Entities, Attributes, Relationships, and Constraints

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16
Q

What is a business rule?

A

A business rule is a brief, precise, and unambiguous description of some policy, procedure, or principle within an organization.

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17
Q

Who developed the relational database model, and when?

A

The relational model was developed by Edgar F. Codd at IBM in 1970. It had problems, in that computers weren’t powerful enough to run it.

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18
Q

Who developed the Entity Relationship Model/Diagram?

A

The ERD was created by Peter Chen in 1976.

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19
Q

Why has the relational model thrived as it has?

A

The relational model is so popular because of:

  • Data Independence (changes in programs don’t require a change in the database)
  • Simple representation of data
  • Easy to use query language
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20
Q

What is a table?

A

A table is a two-dimensional structure composed of rows and columns.

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21
Q

What are the requirements for a “relation”, or a valid table.

A

Every row must be unique
Every attribute value must be atomic (not multivalued)
The order of rows and columns must be irrelevant
Attributes must have unique names

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22
Q

What is a key?

A

A key is one or more attributes that determine other attributes.

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23
Q

What is a primary key?

A

A primary key is an attribute that uniquely identifies a row

24
Q

What is a composite key?

A

A composite key is a primary key that has more than one attribute

25
Q

What is a key attribute?

A

A key attribute is any attribute that is part of a key.

26
Q

What is a foreign key?

A

A foreign key is an attribute whose value(s) match those of the primary key in a related table.

27
Q

What is referential integrity?

A

Referential integrity is when a foreign key contains a value that refers to an existing row in another table.

28
Q

What is a data dictionary?

A

A data dictionary contains metadata, detailed accounting of all the tables in the database, such as attribute names and characteristics for each table in the system.

29
Q

What’s the purpose of a data dictionary?

A

A data dictionary is used to ensure that all design and implementation users use the same tables, attributes and characteristics.

30
Q

What is the idea relationship in a relational database?

A

The one-to-many relationship is the ideal relationship in a relational database.

31
Q

What can be done with a M:N relationship?

A

Generally, a M:N relationship can be taken apart into two 1:M relationships, often with an attribute or a composite entity/bridge entity.

32
Q

In an entity relationship model, what do entities correspond to?

A

Entities correspond with tables in the relational environment.

33
Q

What is the naming convention for entities?

A

Entities are always written in CAPITAL_LETTERS.

34
Q

How are primary keys represented?

A

Primary keys are always underlined.

35
Q

What is the difference between a simple and a composite value?

A

A simple value cannot be subdivided (like gender), where a composite can (address, phone number).

36
Q

What’s the difference between a single-valued and a multi-valued attribute?

A

A single-valued attribute can only have one value (SSN), whereas a multi-value could have multiple (CAR_COLOR, interior or exterior?)

37
Q

What is a derived attribute?

A

A derived attribute is one that could be calculated from other attributes, like age from date of birth.

38
Q

What are the advantages and disadvantages of storing derived attributes?

A

Storing them saves processing, but wastes space.

39
Q

What is cardinality?

A

Cardinality is the expression of the minimum and maximum number of entity occurrences associated with one occurrence of an entity. These are established by business rules.

40
Q

Define “weak relationship”

A

A weak relationship is a non-identifying relationship, that is, a related entity does not contain the primary key of the parent entity within its own primary key.

41
Q

Define “strong relationship”

A

A strong relationship is an identifying relationship, that is, a related entity contains the primary key of the parent entity within its own primary key.

42
Q

What are the conditions of a weak entity?

A

There are two conditions of a weak entity:
It cannot exist without the entity with which it has a relationship.
It has a primary key that is partially or totally derived from the parent entity.

43
Q

What is an example of a weak entity?

A

A weak entity might be the entity DRIVER, which could not exist without the entity CAR.

44
Q

What is an example of a strong entity?

A

A strong entity might be the entity TIRE. It could exist without CAR, or with it.

45
Q

Can a weak entity exist in a strong relationship?

A

Yes. Think of the relationship between COURSE and CLASS. CLASS is a weak entity (no classes without a course), and you wouldn’t imagine the CLASS not to have the COURSE_ID in it, right?

46
Q

What is a unary relationship?

A

A unary relationship is a recursive relationship, that is, a relationship with itself. Think of how EMPLOYEEs can manage one another as needed. This is unary.

47
Q

What is a ternary relationship?

A

A ternary relationship is a relationship between three entities.

48
Q

When are composite entities used? Hell, what are they?

A

Composite entities are used to implement M:N relationships. These entities are composed of the primary keys of each of the entities that are connected. The alternative is adding attributes to the relationship itself, which wasn’t always an option.

49
Q

What is the point of a supertype?

A

A supertype allows for a simplification of a database by representing common relationships and attributes of several classes within one. Subtypes of a supertype inherit its attributes and relationships.

50
Q

What is a subtype discriminator?

A

The subtype discriminator is an attribute within a superclass that determine which subclass an entity fits within.

51
Q

What is the difference between the disjoint/overlapping constraints?

A

A disjoined specialization hierarchy is one where the entity must be ONLY ONE of the subtypes. An overlapping specialization is when it can be multiple.

52
Q

What is the difference between partial and complete constraints?

A

A partial hierarchy is when the entity may be none of the subtypes. A complete is when it must be AT LEAST ONE of the subtypes.

53
Q

What are the conditions of a valid subtype?

A

A subtype is only justified if there is a unique relationship or attribute for each subtype.

54
Q

What is the difference between specialization and generalization?

A

Specialization is the process of identifying entity subtypes by looking at supertypes and working your way down. Generalization is by working from subtypes and identifying their supertypes.

55
Q

What is a natural key?

A

A natural key is a primary key made from a real-world identifier, like a SSN. These can be supplanted by a surrogate key.

56
Q

When is it right to use a composite key?

A

Two primary cases:
When creating a composite entity
As an identifier of a weak entity, when there’s a strong identifying relationship with a parent.

IT 378 - Database Processing (3 decks)

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