Lesson 3 Flashcards
1
Q
Domain
A
In data modeling, the construct used to organize and describe an attribute’s set of possible values.
2
Q
Key
A
One or more attributes that determine other attributes.
3
Q
What are the types of keys?
A
- Superkey
- Candidate key
- Primary key
- Secondary key
- Foreign key
4
Q
Primary key
A
- In the relational model, an identifier composed of one or more attributes that uniquely identifies a row.
candidate key is selected as a unique entity identifier.
5
Q
Determination
The role of a key
A
- In a database table, ‘B determines A’ means that knowing the value of [attribute B] allows you to find the value of [attribute A].
- If [B] is a key, this relationship is special: Each value of [B] uniquely identifies a single record, and thus, a single value of [A].
- This ensures that no two rows have the same value for [B].”
6
Q
Functional dependence
A On B
A
Within a relation R:
An [attribute A] is functionally dependent on an [attribute B] if and only if
- A given value of [attribute B] determines exactly one value of [attribute A].
- The “relationship A is dependent on B” is equivalent to “B determines A,” and is written as B-> A.
7
Q
Determinant
A
Any attribute in a specific row whose value directly determines other values in that row
8
Q
Dependent
A
An attribute whose value is determined by another attribute.
9
Q
Full functional dependence
A
A condition in which an attribute is functionally dependent on a composite key but not on any subset of the key.
10
Q
Composite key
A
A multiple-attribute key
11
Q
Key attributes
A
The attributes that form a primary key
12
Q
Superkey
Every candidate key is a superkey, but not every superkey is a candidate key.
A
- Any combination of columns(attributes) that uniquely identifies a row in a table.
- Think of it like a complete address; it has all the information you need to find a specific location.
13
Q
Candidate key
A
- A candidate key is a minimal superkey.
- It means you can’t remove any columns (attributes) from it, but still have it uniquely identify a row.
Like a shortened address, it has just the essential information to find the location.
14
Q
Entity integrity
A
- A property of a relational table.
- Guarantees each entity has a unique value in a primary key.
- Also that the primary key has no null values.
15
Q
Null
A
- Note that a null is not a blank.
- The absence of an attribute value.
16
Q
Foreign key (FK)
A
An attribute or attributes in one table whose values must match the primary key in another table or whose values must be null.
17
Q
Referential integrity
A
A condition by which a dependent table’s foreign key must have either:
- null entry
- matching entry in the related table
18
Q
Secondary key
A
- A key used strictly for data retrieval purposes.
- For example, customers are not likely to know their customer number (primary key), but the combination of last name, first name, middle initial, and telephone number will probably match the appropriate table row.
19
Q
What are the 3 types of referential integrity rules?
A
- Delete
- Insert
- Update
20
Q
Flags
A
Special codes implemented by designers to trigger a:
- required response
- alert end users to specified conditions
- encode values.
Flags may be used to prevent nulls by bringing attention to the absence of a value in a table.
21
Q
Composite entity
A
- Designed to transform an M:M relationship into two 1:M relationships.
- The composite entity’s primary key comprises at least the primary keys of the entities that it connects.
22
Q
What are the other names that refer to the definition of composite entity?
A
- Bridge entity
- Associative entity
23
Q
Linking table
also known as a junction table or an associative entity
A
Used to implement a many-to-many (M:M) relationship, which is then resolved into two one-to-many (1:M) relationships
24
Q
Index
A
- An ordered array of index key values and row ID values (pointers).
- Indexes are generally used to speed up and facilitate data retrieval.
25
_____ ____ can also be referred to as a index
Index key
26
Unique index
An index in which *the index key* can have only one associated **pointer value** (row).
27
What's the practical significance of taking the **logical view**?
The logical view serves as a reminder of the *simple file concept* of data storage.
28
A **table** can also be thought as?
A persistent representation of a *logical relation*.
29
Why is the order of the rows and columns not important to the DBMS?
- DBMSs don't care about row or column order.
- They use **queries** based on names and values.
- Rearranging them doesn't change the underlying data in the database.
30
**String data** types may not be intended for mathematical manipulation, but can include ___ ?
Character sets that can include *digits or a numeric string*.
31
A candidate key is a ______ superkey without any _______ attributes.
A **candidate key** is a minimal superkey without any unnecessary attributes.
32
Each table _____ represents an attribute.
Column
33
Date attributes contain calendar dates stored in a special format known as the _____ date format.
Julian
34
A table is also called a _____ because the relational model's creator, E. F. Codd, used the two terms as synonyms.
Relation
35
In a relational table, each column has *a specific range of values* known as the ______ domain.
Attribute
36
_____ logic, used extensively in mathematics, provides a framework in which an assertion (statement of fact) can be verified as either true or false.
Predicate
37
Primary keys are required in relational databases to ensure ___.
entity integrity
38
Why is the idea of *unique determination* irrelevant to how databases function?
1. "Determination" isn't unique to databases.
2. It also *exists in math and logic*, where something is _precisely_ defined or fixed.
## Footnote
For example, in a function, the input determines the output.
39
How many types of attributes can determine functional dependence?
*Functional dependencies* can be determined by a single attribute or a combination of multiple **attributes**.
40
If the [attribute (B)] is functionally dependent on a [composite key (A)]; but not on any subset of that composite key, the [attribute (B)] is fully __?
1. Functional Dependency: Attribute B is functionally dependent on attribute A if each value of A determines exactly one value of B.
2. Composite Key: A composite key is a key that consists of two or more attributes.
3. **Full Functional Dependency**: A full functional dependency occurs when an attribute (B) is functionally dependent on a composite key (A), but not on any subset of that composite key.
41
When you press the Enter key or the Tab key to move to the next entry without making a prior entry of any kind.
This creates what?
A NULL is created
42
When can nulls create problems?
1. Variety of the applications- development, software & it's sophistication.
2. When **functions** such as COUNT, AVERAGE, and SUM are used.
43
In the relational model, _____ are important because they are used to ensure that each row in a table is uniquely identifiable.
Keys
44
A _____ is a key that can uniquely identify any row in the table.
Superkey
45
A _____ key can be described as a minimal superkey, a superkey without any unnecessary attributes.
Candidate
46
A _____ is the primary key of one table that has been placed into another table to create a common attribute.
Foreign key
47
A _____ key is defined as a key that is used strictly for data retrieval purposes.
Secondary
48
When you define a table's primary key, the DBMS automatically creates a(n) _____ index on the primary key column(s) you declared.
Unique
49
In a relational model, ____ are also used to establish relationships among tables and to ensure the integrity of the data.
Keys
50
A primary key is a _____ key selected to *uniquely identify all other attribute* values in any given row.
Candidate
51
A table is also called a relation because the relational model's creator, E. F. Codd, used the two terms as __________.
Synonyms
52
A ______ is perceived as a two-dimensional structure composed of rows and columns.
Table
53
The word ______, also known as a dataset in Microsoft Access, is based on the mathematical set theory from which Codd derived his model.
Relation
54
Rows are sometimes referred to as __________.
Records
55
The CUSTOMER table's primary key is CUS_CODE. The CUSTOMER primary key column has *no null entries, and all entries are unique*. This is an example of _____ ______.
Entity Integrity
56
[Referential](https://www.google.com/search?q=Define+Referential#:~:text=containing%20or%20of%20the%20nature%20of%20references%20or%20allusions.) integrity dictates what?
1. That the foreign key must contain values that match the primary key, in the related table
2. Must contain null values.
57
The _____ constraint can be placed on a column to ensure that **every row** in the table has a value for that column.
NOT NULL
58
To avoid nulls, some designers use special codes, known as _____, to indicate the *absence of some value*.
Flags
59
RDBMSs enforce ___ automatically.
integrity rules
60
How is a one-to-many (1:M) relationship implemented in a relational database model?
By putting the foreign key of the "one" side; **in the table** of the "many" side.
61
When are 1:1 relationships necessary in database design? Provide examples.
62
The _____ relationship is the "relational model ideal."
1:M
63
The _____ relationship should be rare in any relational database design.
1:1
64
How do you implement a M:N *relationship*.
Implemented by **creating a new entity** in 1:M relationships *with the original* entities.
65
Another name for a composite entity is a(n) _____ entity.
Bridge
66
The ___ relationship is the relational database norm.
1:M
67
____ relationships cannot be implemented as such in the relational model.
M:N
## Footnote
Many-to-many
68
1. If one department chair "a professor", but can chair only one department.
2. Also the department can have only one department chair.
3. The entities PROFESSOR and DEPARTMENT exhibit a ___ relationship
1:1
69
One characteristic of generalization hierarchies is that they are implemented as ____ relationships.
1:1
70
The proper use of ______ keys is crucial to controlling data redundancy.
Foreign
71
Proper data ________ design requires carefully defined and controlled data redundancies to function properly.
Warehousing
72
What are the database designers two main options when defining a composite table's primary key?
1. use the combination of foreign keys or
2. create a new primary key
73
A(n) _____ is an orderly arrangement used to logically access rows in a table.
Index
74
A ______ index is an index in which the index key can have *only one pointer value* (row) associated with it.
Unique
75
An index key can have multiple _______ (a composite index).
Attributes
