38 Questions
What is the daily amount of videos watched on YouTube?
100 million videos
What is the daily amount of videos added to YouTube?
65,000 videos
What is the minimum amount of terabytes of videos on YouTube?
45 terabytes
What is the amount of extra information YouTube processes daily?
6 petabytes
What is the ranking of NERSC in the world?
No. 1
What is the amount of data stored by NERSC?
2.8 petabytes of data
What is the ranking of YouTube in the list of data storage?
No. 7
How many active customers does Amazon have?
59 million active customers
What is the main purpose of an Enterprise Resource Planning (ERP) system?
To hold all enterprise functions such as manufacturing and finance
What is the primary function of a data warehouse?
To integrate data from various operational databases
What is the advantage of using a data warehouse in an organization like Harrah's?
It helps to understand customer behavior
What is the primary difference between an operational database and a data warehouse?
The purpose of the data
What is an example of a use case for an Enterprise Data Warehouse (EDW) mentioned in the content?
Identifying sales anomalies
What is the size of the largest data warehouse mentioned in the content?
12.1 petabytes (PB)
What is a characteristic of a database mentioned in the history of databases?
It is a collection of connected records
What is the advantage of using an Enterprise Data Warehouse (EDW) in an organization like Wal-Mart?
It helps to identify sales anomalies
What is a fundamental requirement of a relation in a relational model?
Every attribute value must be atomic
What is the primary purpose of a primary key in a relation?
To uniquely identify each row in a relation
What is true about the order of columns in a relation?
It is irrelevant but can be used for indexing
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
What is the purpose of a foreign key in a relation?
To establish a relationship between two relations
What is a characteristic of a relation in a relational model?
Every row must be unique
What is an example of a primary key?
EmployeeID
What is a requirement for a relation to be considered a valid relation?
Every attribute value must be atomic
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
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
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
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
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
What is the purpose of the Delete Rule in Referential Integrity?
To control the deletion of parent and dependent rows
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
Why is the Set-to-Null Delete Rule not allowed for weak entities?
Because it would cause the entity to lose its identity
What type of databases are used by a single user?
Personal databases
What is a characteristic of workgroup databases?
Each member of the workgroup has a computer linked by a network
What is typically found on the client computer in a workgroup database?
The user interface application
What type of databases support the entire organization?
Enterprise applications
What is an example of a large database?
The World Data Center for Climate
Where is the business logic typically found in a workgroup database?
On the application/Web server
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
This quiz covers the characteristics of client-server model in database systems, including personal and workgroup databases. It discusses the advantages and drawbacks of this model, including the distribution of functionality between client computers and the server.
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