M1
Referential
Integrity in a Relational Database
This is where the user doesn’t need to change the data in
more than a single table. For example, if in ‘database 1’ information within a
cell has changed, then this action will automatically mirror that data into
‘database 2,’ without any part on the user. This will be reflected in as many
tables as necessary which are linked.
Primary Keys
A primary key is basically a posh name for ‘reference
number’ like when using telephone banking, you have to type in a personal
number to access your data. It is therefore unique to each person and is more
than often a string of digits. It’s a direct link from a person and their data,
almost like a key.
Foreign Keys
The foreign key or keys is the destination of a
particular relationship, put simply, it groups columns in tables together. It
could occur more than once in a table, but stays are an individual identifier
to the person in question. There can be more than one foreign key as, for
example, a customer has more than one account at a bank, then the Customer ID
could be linked to both the first account and second account, without two separate
Customer ID accounts having to be created.
Expand on the foreign keys explanation.
ReplyDeleteIn a table can there be more than 1 foreign key?
Explain.
M1 achieved
ReplyDeleteI know this is old, but I just don't understand. In our school, we have to write a 2 page report on merits and like 3-4 pages minimum to achieve a distinction! I always surf the internet for other school's students' BTEC work and find such short explanations, but they still achieve whatever grade they're trying to aim for! WTF, it pisses me off so much, like why do I have to write pages and pages of bullshit, and other students can get away with a simple paragraph!?
ReplyDeleteI Understand what you mean. I'm doing this now and amount of work that i have found online with just a few paragraphs and still getting the grade is just unbelievable
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