Database Systems: Client-Server Model

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Questions and Answers

What is the daily amount of videos watched on YouTube?

500 million videos
100 million videos (correct)
200 million videos
50 million videos

What is the daily amount of videos added to YouTube?

30,000 videos
50,000 videos
80,000 videos
65,000 videos (correct)

What is the minimum amount of terabytes of videos on YouTube?

45 terabytes (correct)
30 terabytes
40 terabytes
50 terabytes

What is the amount of extra information YouTube processes daily?

6 petabytes (C) Signup and view all the answers

What is the ranking of NERSC in the world?

No. 1 (A) Signup and view all the answers

What is the amount of data stored by NERSC?

2.8 petabytes of data (A) Signup and view all the answers

What is the ranking of YouTube in the list of data storage?

No. 7 (B) Signup and view all the answers

How many active customers does Amazon have?

59 million active customers (C) Signup and view all the answers

What is the main purpose of an Enterprise Resource Planning (ERP) system?

To hold all enterprise functions such as manufacturing and finance (B) Signup and view all the answers

What is the primary function of a data warehouse?

To integrate data from various operational databases (C) Signup and view all the answers

What is the advantage of using a data warehouse in an organization like Harrah's?

It helps to understand customer behavior (A) Signup and view all the answers

What is the primary difference between an operational database and a data warehouse?

The purpose of the data (A) Signup and view all the answers

What is an example of a use case for an Enterprise Data Warehouse (EDW) mentioned in the content?

Identifying sales anomalies (D) Signup and view all the answers

What is the size of the largest data warehouse mentioned in the content?

12.1 petabytes (PB) (B) Signup and view all the answers

What is a characteristic of a database mentioned in the history of databases?

It is a collection of connected records (A) Signup and view all the answers

What is the advantage of using an Enterprise Data Warehouse (EDW) in an organization like Wal-Mart?

It helps to identify sales anomalies (A) Signup and view all the answers

What is a fundamental requirement of a relation in a relational model?

Every attribute value must be atomic (B) Signup and view all the answers

What is the primary purpose of a primary key in a relation?

To uniquely identify each row in a relation (D) Signup and view all the answers

What is true about the order of columns in a relation?

It is irrelevant but can be used for indexing (B) Signup and view all the answers

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

A simple key is a single field, while a composite key is more than one field (D) Signup and view all the answers

What is the purpose of a foreign key in a relation?

To establish a relationship between two relations (A) Signup and view all the answers

What is a characteristic of a relation in a relational model?

Every row must be unique (B) Signup and view all the answers

What is an example of a primary key?

EmployeeID (C) Signup and view all the answers

What is a requirement for a relation to be considered a valid relation?

Every attribute value must be atomic (A) Signup and view all the answers

What is the purpose of Referential Integrity in a relational database?

To ensure that foreign key values match primary key values in another relation or are null (D) Signup and view all the answers

What happens if you try to delete a customer who has placed orders in the ORDER relation, and the Delete Rule is set to Restrict?

The customer is not deleted, and their orders remain (A) Signup and view all the answers

What happens if you try to delete a customer who has placed orders in the ORDER relation, and the Delete Rule is set to Cascade?

The customer and their orders are deleted (A) Signup and view all the answers

What happens if you try to delete a customer who has placed orders in the ORDER relation, and the Delete Rule is set to Set-to-Null?

The customer is deleted, and their orders are set to null (A) Signup and view all the answers

Can you delete the city Kabul if the CountryCode in City_T does not match any Code in Country_T?

No, the city Kabul cannot be deleted because it does not match any Code in Country_T (D) Signup and view all the answers

What is the purpose of the Delete Rule in Referential Integrity?

To control the deletion of parent and dependent rows (C) Signup and view all the answers

What happens if you try to delete the Country Afghanistan and the Delete Rule of this Foreign Key is set to Cascade?

The Country Afghanistan and all related cities are deleted (A) Signup and view all the answers

Why is the Set-to-Null Delete Rule not allowed for weak entities?

Because it would cause the entity to lose its identity (A) Signup and view all the answers

What type of databases are used by a single user?

Personal databases (C) Signup and view all the answers

What is a characteristic of workgroup databases?

Each member of the workgroup has a computer linked by a network (C) Signup and view all the answers

What is typically found on the client computer in a workgroup database?

The user interface application (A) Signup and view all the answers

What type of databases support the entire organization?

Enterprise applications (C) Signup and view all the answers

What is an example of a large database?

The World Data Center for Climate (A) Signup and view all the answers

Where is the business logic typically found in a workgroup database?

On the application/Web server (A) Signup and view all the answers

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Study Notes

Types of Databases

Personal databases
Workgroup databases
Departmental/Divisional databases
Enterprise applications (transactional)
Data warehousing implementations

Characteristics of Workgroup Databases

Each member of the workgroup has a computer
They are linked by means of a network
Each computer has a copy of the user interface application (client)
The database is on the server

How Large are Typical Databases?

World Data Center for Climate: 220 terabytes of data
NERSC: 2.8 petabytes of data
AT&T: 323 terabytes of information
YouTube: 6 petabytes worth of extra information, 100 million videos watched per day, 65,000 videos added each day
Amazon: 59 million active customers, more than 42 terabytes of data

What do we do with a Database?

Recording every single event that may take place in an organization
Contain the current operational data of the enterprise
Used in Enterprise Resource Planning (ERP) systems
Used in Data Warehousing implementations

History of Databases

Databases now consist of a collection of records connected to one another through links (pointers)

Relational Model

A relation is a named, two-dimensional table of data
A relation consists of rows (records-instances) and columns (attribute or field)
Requirements: unique name, atomic attribute values, unique rows, unique attribute names, irrelevant column and row order

Relational Model in more details

Keys are special fields that serve two main purposes: primary keys and foreign keys
Keys can be simple (a single field) or composite (more than one field)
Keys are used as indexes to speed up the response to user queries

Primary Keys

Are unique identifiers of the relation
Guarantee that all rows are unique
Examples include employee numbers, social security numbers, etc
Can be simple or Composite

Foreign Keys

Referential Integrity constraint can be used with several rules that protect the integrity of data
Delete Rules: Restrict, Cascade, Set-to-Null

Referential Integrity

A rule that states that either each foreign key value must match a primary key value in another relation or the foreign key value must be null

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