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What are the possible connectivities? (Cardinality)

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1. One to one (1:1)
2. One to many (1:N)
3. Many to one (M:1)
4. Many to many (M:N)

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What is a DBMS?

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Database Management System

(A DBMS is also often referred to simply as a database system.)

A DBMS is specialised software which is responsible for efficient storage and retrieval of large amounts of data in a database, allowing it to persist over long periods of time.

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What are integrity constraints?

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Logical statements that restrict the set of allowable relations in a database

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What are the different types of Attributes?

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Key Attribute

Composite Attribute

Single valued attribute

Multi-valued Attribute     

Stored attribute

Derived attribute

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A data model consists of three components. What are they?

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  • Structural part
  • Integrity part
  • Manipulative part – declarative or procedural. This includes querying and updates, manipulating databases
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What is a "Key", and what are the 5 types? (+1 point if you get the bonus one!)

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Keys are an attribute or set of attributes which helps you to identify a row(tuple) in a relation (table)
- They allow you to find the relation between two tables


5 types of keys:

- Candidate key
- Primary Key
- Alternate Key
- Super Key
- Foreign Key


- Surrogate key- If you don’t have a candidate key(CK) in a relation(table), the system will create a temporary key, which is the surrogate.

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What is a candidate key?

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  • The minimal set of attributes that can uniquely identify a tuple(row) is known as a candidate key.
  • The value of the Candidate Key is unique and non-null for every tuple
  • All are “prime attributes.” Same as candidate key.
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What is meant by "Data Independence"?

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Changes at one level of abstraction should not require changes at higher levels.

  • Physical data independence – the physical level may be changed without affecting the logical level.
  • Growth independence - the independence of the view level from the addition of new structures to the database.
  • * Deletions of structures at the logical level disrupt views that reference them
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Instances and Schemas

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  • Databases change over time as information is inserted and deleted
  • The collection of data stored in a database at any moment in time is called an instance of the database
  • The overall design of the database is called the database schema
  • Schemas change infrequently
  • Physical schemas describe databases at the physical level
  • Logical schemas describe databases at the logical level
  • Schemas at the view level are sometimes called subschemas
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What is a Super Key?

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  • The set of attributes that can uniquely identify a tuple(row) is known as a Super Key
  • Two keys together that create a unique attribute is a super key
  • “Adding zero or more attributes to the candidate key generates the super key
  • You can say every candidate key is a super key, but vice versa is not true.
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What is an Entity-Relationship(ER) Model?

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An entity-relation model (ER model) describes the structure of a database with the help of a diagram(logical structure of the database), which is known as an Entity Relationship Diagram(ER Diagram)


  • An ER model is a design or blueprint of a database that can later be implemented as a database
  • The main components of ER model are: Entity Set and Relationship Set
  • It is an example of a conceptual(high-level) data model
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One desirable property of relational database design is that the relation schemas should preserve dependencies. 


What does it mean to say that a design is dependency preserving?

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A design is dependency preserving if the satisfaction of all functional dependencies can be checked “locally”, i.e., by considering each individual relation in turn.

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Q:

What are the possible connectivities? (Cardinality)

A:

1. One to one (1:1)
2. One to many (1:N)
3. Many to one (M:1)
4. Many to many (M:N)

Q:

What is a DBMS?

A:

Database Management System

(A DBMS is also often referred to simply as a database system.)

A DBMS is specialised software which is responsible for efficient storage and retrieval of large amounts of data in a database, allowing it to persist over long periods of time.

Q:

What are integrity constraints?

A:

Logical statements that restrict the set of allowable relations in a database

Q:

What are the different types of Attributes?

A:

Key Attribute

Composite Attribute

Single valued attribute

Multi-valued Attribute     

Stored attribute

Derived attribute

Q:

A data model consists of three components. What are they?

A:
  • Structural part
  • Integrity part
  • Manipulative part – declarative or procedural. This includes querying and updates, manipulating databases
Mehr Karteikarten anzeigen
Q:

What is a "Key", and what are the 5 types? (+1 point if you get the bonus one!)

A:

Keys are an attribute or set of attributes which helps you to identify a row(tuple) in a relation (table)
- They allow you to find the relation between two tables


5 types of keys:

- Candidate key
- Primary Key
- Alternate Key
- Super Key
- Foreign Key


- Surrogate key- If you don’t have a candidate key(CK) in a relation(table), the system will create a temporary key, which is the surrogate.

Q:

What is a candidate key?

A:
  • The minimal set of attributes that can uniquely identify a tuple(row) is known as a candidate key.
  • The value of the Candidate Key is unique and non-null for every tuple
  • All are “prime attributes.” Same as candidate key.
Q:

What is meant by "Data Independence"?

A:

Changes at one level of abstraction should not require changes at higher levels.

  • Physical data independence – the physical level may be changed without affecting the logical level.
  • Growth independence - the independence of the view level from the addition of new structures to the database.
  • * Deletions of structures at the logical level disrupt views that reference them
Q:

Instances and Schemas

A:
  • Databases change over time as information is inserted and deleted
  • The collection of data stored in a database at any moment in time is called an instance of the database
  • The overall design of the database is called the database schema
  • Schemas change infrequently
  • Physical schemas describe databases at the physical level
  • Logical schemas describe databases at the logical level
  • Schemas at the view level are sometimes called subschemas
Q:

What is a Super Key?

A:
  • The set of attributes that can uniquely identify a tuple(row) is known as a Super Key
  • Two keys together that create a unique attribute is a super key
  • “Adding zero or more attributes to the candidate key generates the super key
  • You can say every candidate key is a super key, but vice versa is not true.
Q:

What is an Entity-Relationship(ER) Model?

A:

An entity-relation model (ER model) describes the structure of a database with the help of a diagram(logical structure of the database), which is known as an Entity Relationship Diagram(ER Diagram)


  • An ER model is a design or blueprint of a database that can later be implemented as a database
  • The main components of ER model are: Entity Set and Relationship Set
  • It is an example of a conceptual(high-level) data model
Q:

One desirable property of relational database design is that the relation schemas should preserve dependencies. 


What does it mean to say that a design is dependency preserving?

A:

A design is dependency preserving if the satisfaction of all functional dependencies can be checked “locally”, i.e., by considering each individual relation in turn.

Database Management

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