Data Bases Flashcards
What is a database
AND
why are they used
A data base is a series of organised data
used because:
- doesnt take up a lot of room
- can be easily edited
what is a flat file data base and what are the problems associated with them
Database with only one table
problem:
data duplication which results in greater chance of human error
what is a relational database
Database with many linked tables
Name and describe the tpyes of validation
Range: checks data is within a limit
e.g cost > 0 AND cost
Name and describe the field keys
Primary: a unique identifier
Foreign: used to link tables together
Compound: combines more than one field to make a unique value
What are the different types of data base relationships
- one to one
- one to many
- many to many
A many to many relationship is bad. How can it be overcome
Create new table to allow relationship to become one to many
Why would a database form be used
Reduces entry errors
How do we perform a query
Tablename.Fieldname and criteria = X
Example:
Dog.Dogname and criteria = Olly
Name two database functions
Sum
IFF
What is the sum function used for
Total the values in a numerical field
What is the IFF function used for
Determines if an expression is true or false
Why are database reports used
To summarise and present data in a table
