Databases Design and Development Flashcards
End User Requirements
The requirements are what the users expect to be able to do using the database.
Functional Requirements
Processes that the database system has to be able to do.
What does ER stand for in ER diagrams
Entity Relationship
What are ER diagrams used for ?
Used to represent the relationship between tables.
One-to-Many Cardinality
When one table can be present in many other tables.
You also need a verb to describe the relationship.
3 types of validations in a database
- Length Check
- Range Check
- Restricted Choice
- Presence Check
- Lookup
Presence Check
When a field cannot be left empty, the primary key must have a presence check
Length Check
Set number of characters that can be entered.
Eg; phoneNumber = 11
Restricted Choice
Can only choose a limited selection of options
Eg Countries In The UK
Range Check
Numbers only
When the number needs to be within a range
Eg HotelRating = 1 - 5
What is Referential Intergrity ?
Whenever a Foreign Key is used, it must reference a valid and existing Primary Key in the first table.
Can be used to cascade changes made to the database.
GDPR ensures the data held must be:
Must be accurate Held Securely Not kept longer than necessary Processed lawfully Used for declared purpose only
Search a record in SQL
SELECT
FROM
WHERE
Sorting a record in SQL
SELECT
FROM
WHERE
ORDER BY (DESC or ASC)
Why are two tables created ?
To avoid data duplication and anomalies
