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Database Concepts Design Midterm > Flashcards > Flashcards

Flashcards

1
Q

What is an Entity Relationship Model (ERM)?

A

A data model that describes relationships among entities at the conceptual level.

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2
Q

What is an Entity Relationship Diagram (ERD)?

A

A diagram that depicts an ERM’s entities, attributes, and relations.

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3
Q

What are the five major parts of a database management system (DBMS)?

A

Hardware, software, people, procedures, and data.

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4
Q

What is a hierarchal model?

A

An early database model whose basic concepts and characteristics formed the basis for subsequent database development. This model is based on an upside-down tree structure in which each record is called a segment and has a 1:M relationship to the segment directly below it.

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5
Q

What is a network model?

A

An early data model that represented data as a collection of record types in 1:M relationships.

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6
Q

What is a relational model?

A

It represents data as independent relations. Each relation (table) is conceptually represented as a two-dimensional structure of intersecting rows and columns. The relations are related to each other through the sharing of common entity characteristics (values in columns).

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7
Q

What is an object-oriented model?

A

A data model whose basic modeling structure is an object.

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8
Q

What is an extended relational data model?

A

A model that includes the object-oriented model’s best features in an inherently simpler relational database structural environment.

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9
Q

What types of relationships does an ERM/ERD show?

A

One to one (1:1), one to many (1:M), and many to many (M:N)

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10
Q

What is determination?

A

The state in which knowing the value of one attribute makes it possible to determine the value of another.

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11
Q

What is a functional dependency?

A

The value of one or more attributes determines the value of one or more other attributes.

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12
Q

What is a determinant?

A

In a functional dependency, it’s the attribute or group of attributes whose value determines another.

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13
Q

What is a dependent?

A

In a functional dependency, it’s the attribute whose value is determined by the other attribute(s).

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14
Q

What is a full functional dependency?

A

A functional dependency in which the entire collection of attributes in the determinant is necessary for the relationship.

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15
Q

What is an existence-dependency?

A

A property of an entity whose existence depends on one or more other entities.

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16
Q

What is a primary key?

A

An attribute or combination of attributes that uniquely identifies each row in a table.

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17
Q

What is a composite key?

A

A key that is composed of more than one attribute.

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18
Q

What is a superkey?

A

A key that can uniquely identify any row in the table. It functionally determines every attribute in the row.

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19
Q

What is a candidate key?

A

A superkey without any unnecessary attributes. It’s based on a full functional dependency.

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20
Q

What is a foreign key?

A

The primary key of one table that has been placed into another table to create a common attribute.

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21
Q

What is a secondary key?

A

A key that is used strictly for data retrieval purposes and does not require a functional dependency.

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22
Q

What is a surrogate key?

A

A system defined attribute created and managed via the DBMS. It’s used when the primary key is considered unsuitable.

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23
Q

How does a relational database implement relationships between tables?

A

By having another table’s primary key as a foreign key.

24
Q

What are the different notations that an ERD uses to show relationships?

A

Chen, Crow’s Foot, and UML Class Diagram.

25
Q

What is unstructured data?

A

Data that exists in its original, raw state; that is, in the format in which it was collected.

26
Q

What is structured data?

A

Data that has been formatted to facilitate storage, use, and information generation in a predefined data model.

27
Q

What is semistructured data?

A

Data that has already been processed to some extent.

28
Q

What is data inconsistency?

A

A condition in which different versions of the same data yield different (inconsistent) results.

29
Q

What is a query?

A

A specific request to a DBMS to read or update data.

30
Q

What is a business rule?

A

A brief, precise, and unambiguous description of a policy, procedure, or principle within a specific organization.

31
Q

What does a relational set operator do?

A

It uses relational algebra operators on existing relations (tables) and produces new relations.

32
Q

Define SELECT (aka RESTRICT)

A

It’s a unary operator that yields values for all rows found in the table that satisfy a given condition.

33
Q

Define PROJECT

A

It’s a unary operator that yields all values for selected attributes.

34
Q

Define UNION

A

It combines all rows from two tables, excluding duplicate rows. The tables must have the same attribute characteristics.

35
Q

Define INTERSECT

A

It yields only the rows that appear in both tables.

36
Q

Define DIFFERENCE

A

It yields all rows in one table that are not found in the other table; that is, it subtracts one table from the other.

37
Q

Define PRODUCT

A

It yields all possible pairs of rows from two tables—also known as the Cartesian product.

38
Q

Define JOIN

A

It allows information to be intelligently combined from two or more tables.

39
Q

What does a natural join do?

A

Links tables by selecting only the rows with common values in their common attribute(s).

40
Q

What does an equijoin do?

A

Links tables on the basis of an equality condition that compares specified columns of each table.

41
Q

What does an inner join do?

A

Only returns matched records from the tables that are being joined.

42
Q

What does an outer join do?

A

The matched pairs are retained, and any unmatched values in the other table are left null.

43
Q

Define DIVIDE

A

It answers queries about one set of data being associated with all values of data in another set of data.

44
Q

What is cardinality?

A

The maximum and minimum number of entity occurrences associated with one occurrence of the related entity.

45
Q

What is a schema?

A

The conceptual organization of the entire database as viewed by the database administrator.

46
Q

What is a subschema?

A

It defines the portion of the database “seen” by the application programs that actually produce the desired information from the data within the database.

47
Q

What is a partial dependency?

A

A functional dependency where an attribute is dependent only on part of the primary key.

48
Q

What is a transitive dependency?

A

A functional dependency where an attribute is dependent on an attribute that isn’t part of the primary key.

49
Q

What is a repeating group?

A

It happens when multiple entities of the same type exist for any single key attribute occurence.

50
Q

What does it mean when data is in first normal form (1NF)?

A

The data is in table format, there are no repeating groups, and the primary key is identified.

51
Q

What does it mean when data is in second normal form (2NF)?

A

The data is in 1NF and there are no partial dependencies.

52
Q

What does it mean when data is in third normal form (3NF)?

A

The data is in 2NF and there are no transitive dependencies.

53
Q

What does it mean when data is in Boyce-Codd normal form?

A

The data is in 3NF and every determinant is a candidate key (special case of 3NF).

54
Q

What does it mean when data is in fourth normal form (4NF)?

A

The data is in BCNF and there are no independent multivalued dependencies.

55
Q

What does it mean when data is in fifth normal form (5NF)?

A

The data is in 4NF and cannot have lossless decomposition into smaller tables.

Database Concepts Design Midterm (1 decks)

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