databases nat 5 Flashcards
What is a presence check?
A presence check ensures that data is entered into a field and not to be left blank.
What is restricted choice
The user has to pick from a [re=set list of options.
- e.g year group s1, s2, s3
What is a length check
Field length validation limits the number of characters that can be stored in a field
e.g >6 for passwords
What is a range check
Data has an upper and/ or lower acceptable limit
e.g >1 and <100
What is a unique check
Data entered in the field must not be the same as any other record. Used for primary keys.
What is a look-up???
Used for all foreign keys. It ensures a foreign key exists as a primary key in another file.
i.e., referential integrity.
What is the DIFFERENCE between VERIFICATION & VALIDATION????
Validation makes sure that the data entered is acceptable and sensible
whereas
a verification ensures data entered is correct by asking the user to enter the data twice. NOT full proof.
What is the DIFFERENCE between a FLAT-FILE DATABASE and RELATIONAL DATABASES
Relational/ linked databases are used to store info about several topics
whereas
a flat file database is used to store info about 1 topic, not linked to ANY OTHER database
Primary key definition
A field of any data type, which uniquely identifies one record in a file/ table
Foreign key definition
A field in a table which is a primary key in another table. It is used to link the tables. Always validated using a LOOKUP
Record definition
A record stores info on one person or thing in the topic
AKA row
e.g a pupil
a school
a car
a cartoon
File definition
A file stores information on 1 topic
AKA table or entity
e.g
pupils
schools
cars
cartoons
Field definition
A field stores one single piece of info about the person or thing in the topic aka column or attribute
e,g
school name
registration class
registration number
ok that’s it
Text
letters, words, symbols
Numeric
numbers
