C175 Data Management Foundations > Lesson 4 Database Design > Flashcards

Lesson 4 Database Design Flashcards

(187 cards)

Study These Flashcards
1
Q

binary relationship

A

An ER term for an association (relationship) between two entities.

For example, PROFESSOR teaches CLASS.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

cardinality

A
  • A property that assigns a specific value to connectivity
  • expresses the range of allowed entity occurrences associated with a single occurrence of the related entity.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

composite attribute

For example, a phone number such as 615-898-2368 may be divided into an area code (615), an exchange number (898), and a four-digit code (2368).

A

An attribute that can be further subdivided to yield additional attributes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

composite identifier

also known as a composite key

A

In ER modeling, a key composed of more than one attribute.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

derived attribute

A
  1. An attribute that does not physically exist within the entity and is derived via an algorithm.
  2. For example, the YEARS_EMPLOYED attribute might be derived by subtracting the start date from the current date.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

existence-dependent

A
  1. A property of an entity whose existence depends on one or more other entities.
  2. In such an environment, the existence-independent table must be created and loaded first, because the existence-dependent key cannot reference a table that does not yet exist.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

existence-independent

A
  • A property of an entity that can exist apart from one or more related entities.
  • Such a table must be created first when referencing an existence-dependent table.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

identifiers

A

One or more attributes (columns) that uniquely identify each entity instance.

also known as keys

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

iterative process

A

A process based on repetition of steps and procedures.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

mandatory participation

A

A relationship in which one entity occurrence must have a corresponding occurrence in another entity.

  1. For example, an EMPLOYEE works in a DIVISION.
  2. A person cannot be an employee without being assigned to a company’s division.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

multivalued attributes

A

An attribute that can have many values for a single entity occurrence.

  1. For example, an EMP_DEGREE attribute might store the string "BBA, MBA, PHD" to indicate three different degrees held.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

non-identifying relationship

A

A relationship in which the the child table’s primary key is independent of the parent table’s primary key.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

optional attribute

A

In ER modeling, an attribute that does not require a value; therefore, it can be left empty.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

optional participation

A

In ER modeling, a condition in which one entity occurrence does not require a corresponding entity occurrence in a particular relationship.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

participants

A
  • An ER term for entities that participate in a relationship.

  • For example, in the relationship “PROFESSOR teaches CLASS,” the teaches relationship is based on the participants PROFESSOR and CLASS.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

recursive relationship

A

A relationship found within a single entity type.

  1. For example, an EMPLOYEE is married to an EMPLOYEE or
  2. A PART is a component of another PART.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

relational schema

A

The organization of a relational database as described by the database administrator.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

relationship degree

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

required attribute

A

In ER modeling, an attribute that must have a value.

In other words, it cannot be left empty.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

simple attribute

A

An attribute that cannot be subdivided into meaningful components.

Compared to composite attribute.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

single-valued attribute

A

An attribute that can have only one value.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

strong (identifying) relationship

A
  1. This relationship exists whenever the primary key of the related entity contains the primary key components of the parent entity.
  2. A relationship that occurs when two entities are existence-dependent.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

strong entity

A
  • An entity that is existence-independent.
  • It can exist apart from all of its related entities.

Also called a regular entity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

ternary relationship

A
  • An ER term used to describe an association (relationship) between three entities.
  • For example, a DOCTOR prescribes a DRUG for a PATIENT.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
unary relationship
- An ER term used to describe an association _within_ an entity. - For example, an EMPLOYEE might manage another EMPLOYEE.
26
weak entity
- An entity that displays existence dependence and *inherits the primary key of its parent entity*. - For example, a DEPENDENT requires the existence of an EMPLOYEE.
27
weak relationship
- A relationship in which *the PK of the related* entity **does not contain** a PK component of the parent entity. - A weak relationship links two strong entities that can exist independently.
28
Is the entity relationship model (ERM); dependent on the database type?
No, the ERM is not dependent on the database type; it serves as a conceptual framework for organizing data regardless of the specific database implementation
29
Why is The *Crow's Foot notation* more implemented than the Chen notation.
1. CF Notation symbols *directly translate to database concepts* like relationships (one-to-many, etc.) 2. Offers simplicity visualization of data structures. 3. This makes it **easier to map** diagrams to database tables compared to the more *abstract Chen notation*.
30
An *entity* in the *entity relationship model* corresponds with $ ?
Entities in ER models corresponds to a **table** in the relational environment.
31
What does a table row represent in the entity relationship model?
A table row represents a **single entity instance**, containing all attributes *for that specific occurrence* of the entity.
32
In the Chen and Crow's Foot notations, an entity is represented with ?
Entity: a **rectangle** containing the entity's name
33
In the original Chen notation how are attributes & attribute names represented?
- Each attribute is represented by an oval - The attribute name connected to an entity rectangle with a line.
34
Why do Software vendors oppose the *Chen representation*?
- Software vendors may not favor Chen notation because it can be visually complex and use _many_ symbols, potentially *making it harder to use and less appealing* to a wider audience. - This complexity can lead to larger diagrams and a steeper learning curve
35
What characterizes a composite identifier in database design?
A composite identifier is a primary key that consists of more than one attribute *used to uniquely identify an entity instance*.
36
Why is *Crow's Foot notation* useless for multi variable **attributes**?
1. CF notation *focuses on relationships* between entities. 2. It uses symbols to represent _cardinality_ and _optionality_ (mandatory or optional) in relationships. 3. **Multi valued** attributes are about a single entity. ## Footnote cardinality (one-to-one, one-to-many, etc.)
37
How does Composite attributes make it easier to facilitate detailed queries?
1. They **group** related information together. 2. Instead of searching through separate fields for each part of an address,*you can use the composite "address" attribute to find exactly what you need with a single query*. 3. This makes queries more efficient and easier to formulate.
38
Do **relationships** between entities operate in only one direction?
No, relationships between entities can operate in both directions, allowing for interactions that can be navigated from either entity involved.
39
What establishes connectivities and cardinalities in database relationships?
Connectivities and cardinalities are established by concise statements known as **business rules** that define how entities relate to each other.
40
Is there any way to represent cardinality in Chen notation?
Chen notation includes methods to represent cardinality through **specific symbols** that indicate relationships between entities.
41
What does it mean for an entity to have a *mandatory primary key* in implementation terms?
1. A mandatory primary key means that *every record* in a database table must have a *unique identifier*. 2. This ensures that each entry can be *easily distinguished* from others, preventing confusion and duplication.
42
Under what conditions does a weak relationship exist in database design?
A weak relationship exists if the PK of the related entity **does not contain** any PK *components of the parent* entity.
43
In a **1:M** relationship, what must be done to avoid *referential integrity errors*?
To avoid referential integrity errors in a 1:M relationship, the *data of the "1" side must be **loaded first**,* ensuring that reference entities are in place.
44
Are unary relationships common in manufacturing industries?
Yes, unary relationships, *where an entity relates to itself*, are common in manufacturing industries and can represent scenarios such as employee management hierarchies.
45
Define both **participation** & **referential integrity**; are they bidirectional in a relationship?
1. Participation relates to *whether an entity requires a relationship with another* & does not necessarily imply a bidirectional requirement 2. Referential integrity ensures that *such references are valid* and also do not necessarily imply a bidirectional requirement.
46
When does a weak relationship, also known as a non-identifying relationship, exist?
A weak relationship exists if the primary key of the related entity *does not incorporate any primary key components from the parent entity*, indicating a lack of identity dependency.
47
What does the existence of a **mandatory relationship** suggest about *minimum cardinality*?
A *mandatory relationship* indicates: That its minimum cardinality *must be at least 1* for the **mandatory entity**, not 0
48
Why must a database designer understand the “1” and “M” sides of each relationship when implementing a **small database**?
Understanding the “1” and “M” sides is crucial for proper relational design, as it determines *how entities reference each other* and ensures integrity within the database.
49
The _____ notation of entity-relationship modelling can be used for both *conceptual and implementation* modelling.
UML
50
The entity relationship diagram **(ERD)** represents the _____ database as *viewed by the end user*.
conceptual
51
A(n) _____ is the *set of possible values* for a given attribute.
domain
52
_Ideally_, an entity *identifier* is composed of _____ attribute(s)
one
53
A _____ attribute can be further subdivided to yield additional attributes.
composite
54
A _____ attribute is one that cannot be subdivided.
simple
55
The **conceptual model** can handle _____ relationships and multivalued attributes.
M:N
56
A derived attribute is indicated in the Chen notation by a _____ that *connects the attribute and an entity*.
dashed line
57
The __________ attribute *need not be* physically stored within the database.
derived
58
A relationship is an association between _____.
Entities
59
What does cardinality express?
Cardinality expresses the minimum and maximum number of **entity occurrences** associated with *one occurrence of the related entity*.
60
When the specific cardinalities are not included on the diagram in Crow's Foot notation, cardinality is implied by the use of _____.
symbols
61
Knowing the minimum and maximum number of _____ occurrences is very helpful at the *application software level*.
entity
62
An entity is said to be _____ -dependent if it can *exist in the database only when* it is **associated** with another related entity occurrence.
existance
63
If an entity can exist apart from all of its related entities, then it is existence-independent, and it is referred to as a(n) _____ entity.
strong
64
A weak entity does not have $ attributes to form a $.
1. sufficient 2. Primary key
65
The existence of a(n) _____ entity indicates that its *minimum cardinality* is zero.
optional
66
The Crow's foot symbol with two vertical parallel lines indicates _____ cardinality.
(1:1)
67
A _____ relationship exists when an association is maintained within a single entity.
unary
68
A _____ relationship exists when three entities are associated
ternary
69
If an employee within an EMPLOYEE entity has *a relationship with itself*, that relationship is known as a _____ relationship.
recursive
70
To simplify the conceptual design, most *higher-order relationships* are decomposed into appropriate equivalent _____ relationships whenever possible.
binary
71
The entity relationship model uses the **associative entity** to represent a(n) _____ relationship between two or more entities.
M:N
72
When using the Crow's Foot notation, the associative entity is _indicated by_ _____ relationship lines between the *parents and the associative entity*.
solid
73
______ are charcteristics of entities
Attribute
74
A _____ attribute is an attribute that must have a value
required
75
______ are underlined in an ER diagram
Identifiers
76
A person's Social Security number would be an example of a ______ ______ attribute.
Single valued
77
A ______ attribute need not be physically stored within the database.
derived
78
A _____ attribute is an attribute that can be further subdivided to yield additional attributes.
composite
79
When indicating cardinality, the first value represents the _____ number *of associated entities*.
minimum
80
The concept of *relationship strength* is based on how the ______ ______ of a related entity is defined.
primary key
81
A ______ relationship is also known as an identifying relationship.
strong • A strong relationship links a strong entity to a weak entity (the weak entity depends on the strong one).
82
The Crow's Foot notation depicts the **strong relationship** with a(n) _____ line between the entities.
solid
83
A weak entity must be ______ dependent.
existence
84
The Chen notation identifies a *weak entity* by using a double-walled entity ________.
rectangle
85
Participation is _______ ; if one entity occurrence *does not require a corresponding entity occurrence* in a particular relationship.
optional
86
In Crow's Foot notation, an **optional relationship** between entities is shown by drawing a small _____ _____ on *the side of the optional entity*.
small circle/circle (o)
87
________ expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity.
Cardinality
88
A relationship _______ indicates the number of *entities or participants* associated with a relationship.
degree/cardinality
89
Is the process of database design considered sequential?
No, the process of database design is often iterative, involving repetitions and revisions rather than a strictly linear sequence of steps.
90
The first step in building an entity-relationship diagram (ERD) is _____ .
Analysis: creating a detailed **narrative** of the organization's *description of operations*.
91
1. If `Tiny College` has some departments that are classified as "research only" and *do not offer courses*. 2. The `COURSE` entity of the college database would be _____ to; the `DEPARTMENT` entity. ## Footnote *Entity* does mean table
*optional* ## Footnote [Learn more](https://g.co/gemini/share/23a1faa87a58)
92
An ______ process is based on repetition of processes and procedures.
iterative
93
Identifying the *attributes of entities* helps in the better understanding of ______ among entities.
relationships
94
In organizations that *generate large number of transactions*, _____ are often a top priority in database design.
high processing speeds
95
Complex information requirements may $ ?
1. Dictate data transformations OR 2. *Expand the number* of entities and attributes within the designs
96
________ not only helps database designers to stay on track during the design process, it also enables them *to pick up the design thread* when the time comes to modify the design.
Documentation
97
What is an entity type in entity-relationship modeling?
A set of unique individuals ## Footnote Example: The entity type 'Passenger' includes all passengers in the system.
98
What does the relationship type represent in entity-relationship modeling?
A set of related pairs ## Footnote Example: The relationship type 'Passenger-Holds-Booking' represents pairs of passengers and their associated bookings.
99
What is an attribute type?
A *set of values* related to an entity ## Footnote Example: The attribute type 'BookingCode' encompasses all possible booking codes.
100
Define entity instance ## Footnote [Learn more](https://share.evernote.com/note/73ea804a-dda4-3bd5-13f9-3421e8dfc1bc)
An individual member of the entity _type_ ## Footnote Example: 'Muhammed Ali' is a specific entity instance representing a passenger.
101
What is a relationship instance?
A specific assertion about entities ## Footnote [Learn more](https://share.evernote.com/note/73ea804a-dda4-3bd5-13f9-3421e8dfc1bc)
102
What is an attribute instance?
An individual *value related* to an attribute ## Footnote Example: '39240' is a specific instance of the 'BookingCode' attribute. [Learn more](https://share.evernote.com/note/73ea804a-dda4-3bd5-13f9-3421e8dfc1bc)
103
In entity-relationship modeling, what do *entity types, relationship types, and attribute types* correlate to?
Tables, foreign keys, and columns ## Footnote Their instances correspond to rows, foreign key values, and column values, respectively.
104
What is an entity in the context of data management?
A distinct **object or thing** in the domain that *can be identified and has relevance* to the data being managed.
105
What are attributes in *relation to entities*?
Properties or characteristics of an entity that provide more detailed information about it.
106
Define relationships in data management.
Define how entities interact with or relate to one another.
107
How do entities and attributes correlate?
Each entity is *defined by its attributes*, which describe its state or properties.
108
What is the role of relationships between entities?
Relationships connect two or more entities, illustrating how they are interrelated within the data model.
109
In addition to entities, what other things can possess attributes?
In database design, a relationship between two entities can sometimes have its own attributes that describe the relationship itself.
110
What is a weak entity?
An entity that *cannot be uniquely identified by its own attributes* alone and relies on a FK from an identifying table. ## Footnote [Learn more](https://share.evernote.com/note/355058fa-f27d-0e8d-7fab-6ad3549c3cdc)
111
What is an 'IsA' relationship?
A type of relationship that signifies inheritance or a hierarchical connection between entities.
112
What is a primary key?
A column (or set of columns) in a table that uniquely identifies **each row** in that table. ## Footnote [Entity usage](https://share.evernote.com/note/355058fa-f27d-0e8d-7fab-6ad3549c3cdc)
113
What are composite keys?
Keys that consist of two or more columns used together to create a unique identifier for a row in a table. ## Footnote [Weak entity usage](https://share.evernote.com/note/7b76f238-d75c-1983-0cfc-04ca1637a437)
114
What is an artificial key?
A single-column primary key created by the database designer *when no suitable natural primary key exists*. ## Footnote [📖aka Surrogate keys ](https://share.evernote.com/note/41ebe9f5-ffd2-8f15-a396-d338de0f18da)
115
Define a foreign key.
A column (or set of columns) in one table that _refers_ to the *primary key in another table*, establishing a link.
116
In a one-to-one relationship, how is the primary key used?
Table A’s primary key can serve as a foreign key in Table B.
117
What is the relationship between 1:M and FK?
Table `A` has the primary key, which Table `B` references as a foreign key.
118
What is a many-to-many relationship?
A relationship where multiple records in Table `A` can relate to multiple records in Table `B`, often requiring a junction table.
119
What is the purpose of implementing strong entities as tables?
To *create a table* for each strong entity identified in the data model. ## Footnote [📖](https://share.evernote.com/note/200f602a-b640-e16c-df8d-13fa66b555c7)
120
What happens if no suitable primary key exists?
An artificial key is created to serve as the primary key. ## Footnote [📖 Artificial Key](https://share.evernote.com/note/41ebe9f5-ffd2-8f15-a396-d338de0f18da)
121
What is the purpose of implementing subtype entities *as tables*?
To create tables for *subtype entities that inherit* from a main entity.
122
How is a weak entity implemented as a table?
By using a **composite primary key** that includes a foreign key referencing the identifying entity.
123
What does specifying cascade and restrict actions do?
Defines referential integrity actions, for relationships **between tables**.
124
Fill in the blank: In the first step of the logical design phase, each entity becomes a _______ and each attribute becomes a _______.
[table], [column]
125
What is the first step in the *logical design* phase of database design?
Each entity becomes a table and each attribute becomes a column. ## Footnote [📖 Design](https://share.evernote.com/note/1b321a7b-03c7-e146-7287-7b8848bbf8bc)
126
What _must_ *primary keys be* in a database?
Unique and not NULL.
127
What are the three desirable characteristics of primary keys?
* Stable * Simple * Meaningless
128
What do solid bullets (●) denote in table diagrams?
Primary key columns.
129
What defines a strong entity in database design?
Can be uniquely *identified by its own* attributes.
130
What is a weak entity?
Cannot be uniquely identified by its own attributes and relies on a strong entity.
131
What is the *primary key* of a **weak entity** typically composed of?
A weak entity uses a **composite key** including a *foreign key from the identifying strong entity* to make a PK.
132
What types of relationships *can entities* have?
* One-to-One * One-to-Many * Many-to-Many ## Footnote [📖](https://share.evernote.com/note/eeb74326-1792-3c6c-6349-93058d1d32ca)
133
What is a foreign key?
1. A field in a database table refers to a *single piece of information* within a row; representing a **specific attribute** or detail about the data entry within that row. 2. A FK is a **field** in one table that *uniquely identifies a row of another table*.
134
What happens in a many-to-many relationship?
A new dependent table (junction) is created containing two foreign keys. ## Footnote [📖](https://share.evernote.com/note/eeb74326-1792-3c6c-6349-93058d1d32ca)
135
What does **cascade** on *primary key update and delete* mean?
**Foreign keys** that reference a primary key will also update or delete automatically.
136
Can NULLs be allowed in the foreign key column?
Yes, unless the foreign key constraint specifies `NOT NULL`.
137
Are *many-one* and *one-one* relationships always implemented before *many-many* relationships?
1. **Many-to-many** relationships often rely on underlying *one-to-many* relationships to be implemented first. 2. Think of it like building a house – you need the foundation (one-to-many) before you can add the complex roof structure (many-to-many).
138
What kind of relationship is implemented where; a PK of a table implemented is always composite?
- Many-to-many relationships in databases *require a special table* to link two other tables. - This "junction table" uses a *composite primary key* (made up of foreign keys from the two main tables) to ensure each relationship is unique. ## Footnote [📖](https://share.evernote.com/note/eeb74326-1792-3c6c-6349-93058d1d32ca)
139
What is the rule regarding *unique and required attributes* in attribute cardinality?
Each *unique attribute instance* describes [at most one entity instance](https://share.evernote.com/note/3d0ca46a-f349-228d-92cc-4b5fb3ce8f09).
140
What SQL keyword is used for unique attributes?
UNIQUE.
141
What SQL keyword is used for required attributes?
`NOT NULL`
142
What happens to *optional attributes* in a database?
They can have zero instances and _may_ allow `NULL` values.
143
What does the `PRIMARY KEY` keyword enforce?
Unique and required constraints.
144
What does the `FOREIGN KEY` column require in terms of constraints?
`UNIQUE` and `NOT NULL` if derived from unique and required relationships.
145
What SQL command is used to create a table with a primary key?
`CREATE TABLE`
146
What is normalization in database design?
The process of **eliminating redundancy** from *tables created during the implementation* of entities, relationships, and attributes.
147
What is the highest normal form typically aimed for in practical database design?
Boyce-Codd Normal Form (BCNF)
148
Define dependency in the context of database normalization.
Column `A` depends on column `B`; if each `B` value _relates_ to at most one `A` value.
149
What are the three steps involved in **normalizing to BCNF**?
1. List all unique columns 2. Identify dependencies *on non-unique columns* 3. Eliminate dependencies *on non-unique columns*
150
What is denormalization?
Intentionally introducing redundancy by *merging tables to eliminate join queries* and improve query performance.
151
When is **de**normalization **typically considered** in database design?
For tables that experience infrequent data modifications; to enhance `SELECT` queries.
152
What should **designers** do as *tables and keys are specified* in the database design process?
1. Review for BCNF 2. Identify dependencies and unique columns.
153
What should be done if *dependencies are identified*; that do not meet the _uniqueness_ criteria?
Decompose tables *into smaller tables* that meet BCNF requirements.
154
Originally, normalization referred to achieving _______.
first normal form
155
What is the purpose of **identifying dependencies** on non-unique columns during normalization?
To eliminate redundancy by *decomposing* tables.
156
Why is Denormalization less preferred in database design.
- Denormalization introduces redundancy to speed up reads. - The best choice depends on whether your priority is *data consistency* or read performance.
157
What does Crow's Foot notation primarily represent?
Entity-relationship models in database design.
158
How is Chen notation less detailed than Crow's Foot notation.
1. Chen notation , it tends to be _less_ detailed regarding the **nature of relationships**, *such as cardinality or specific constraints*, which can lead to ambiguity in larger or more complex designs. 2. Crow's Foot Notation, on the other hand, provides for designers needing a **comprehensive view** of relationships and constraints in their data models.
159
In Crow's Foot notation, what symbol represents a one-to-many relationship?
A line ending with a crow's foot symbol (three prongs).
160
What shape is used to represent entities in Chen notation?
Rectangles.
161
In Chen notation, attributes are represented by _______.
Ovals/Ellipses.
162
What does a diamond shape represent in Chen notation?
A relationship.
163
What common visual feature is absent in Crow's Foot notation?
Colors
164
What is the primary purpose of using entity-relationship diagrams?
To visually represent the data structure and relationships within a database.
165
In Crow's Foot notation, a single line represents?
a one-to-one relationship
166
What does the '0..1' notation indicate in Crow's Foot?
An optional relationship where an entity can exist without a corresponding entity. ## Footnote [Determining optionality](https://g.co/gemini/share/52b5453d1bdf)
167
Short Answer: Name one advantage of using Chen notation over Crow's Foot notation.
Chen notation provides a more detailed representation of attributes and relationships.
168
In Crow's Foot notation, a relationship with a maximum of five occurrences is represented as _______.
1..5 ## Footnote [1..5 V 1..N](https://g.co/gemini/share/8c22c1201716)
169
Which notation is more widely used in software engineering?
Crow's Foot ## Footnote [📖](https://share.evernote.com/note/eeb5e850-b5eb-e4c7-a905-8bdcc61aeb91)
170
**Chen notation** can represent more than just *weak entities*. It's a visual way to design databases, showing:
* Entities and Attributes: Rectangles for entities, with attributes listed inside. * Relationships: Diamonds show how entities connect. * Cardinality/Participation: Symbols indicate how many entities participate in a relationship. * Weak Entities: Double-lined rectangles for weak entities. * Inheritance: Models entities inheriting attributes from a parent entity.
171
What is the significance of a dashed line in Crow's Foot notation?
It indicates a non-identifying relationship.
172
Short Answer: How are multi-valued attributes represented in Chen notation?
By using a double ellipse.
173
In Crow's Foot notation, what does a double line indicate?
**mandatory relationship** is indicated by a solid vertical line (perpendicular to the relationship line) next to the entity.
174
Which notation is generally considered simpler for beginners?
Crow's Foot
175
In Chen notation, a weak entity is represented by a _______.
Double rectangle.
176
True or False: Crow's Foot notation uses colors to differentiate between types of relationships.
False
177
What does '1..*' signify in Crow's Foot notation?
A one-to-many relationship where one entity can relate to many others.
178
What is a primary key in the context of entity-relationship diagrams?
An attribute or set of attributes that **uniquely identifies** an entity.
179
Relationships in Chen notation are represented by _______.
Diamonds.
180
What is the main difference between cardinality and participation in Crow's Foot notation?
1. Cardinality _specifies_ the number of instances. 2. Participation indicates *whether an entity's existence* is dependent on another.
181
In which notation are relationships explicitly labeled with verbs?
In **CFN** Verbs are often used to label the relationships, making them explicit.
182
Crows Foot uses symbols to label relationships, which in turn represent?
Crow's Foot notation uses symbols to represent *cardinality and optionality*.
183
1. Determine the Maxima and Minimum 2. 1(1)
`singular - required`
184
1. Determine the Maxima and Minimum 2. 1(0)
`singular - optional`
185
1. Determine the Maxima and Minimum 2. M(1)
`plural - required`
186
1. Determine the Maxima and Minimum; is it Unique? 2. 1-1(1)
Unique `singular - required` ## Footnote In ER diagrams, 1 indicates a unique attribute and M indicates a non-unique attribute.
187
1. Determine the Maxima and Minimum; is it Unique? 2. M-M(0)
Not Unique `plural - optional` ## Footnote In ER diagrams, 1 indicates a unique attribute and M indicates a non-unique attribute.
C175 Data Management Foundations
flashcards
Decks in class (31)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions