Keys and Relationships Flashcards

1️⃣ Familiarise yourself with the flashcards:

Look through all the flashcards to see what's on both sides.
Make sure you understand the information on each card. If something's unclear, click the link to the revision notes at the bottom of the page for more details.

2️⃣ Test yourself:

Look at the question or prompt on each card and try to remember the answer before flipping it over.
Check the answer and make a note of any cards you find challenging and need to go over more.

3️⃣ Consistently Review and Practice:

Use spaced repetition: spend more time on the cards you struggle with and go over them more often.
Regularly review all the flashcards to help you better understand and retain the information over time.

Note: We may include questions that have multiple correct answers. It's useful to remember specific examples to understand these concepts better.

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What is a primary key?

A field that makes each record unique in a table.

It keeps records unique and lets other tables link to them.

A field in one table that stores a primary key from another table to make a link.

A rule that a foreign key must match an existing primary key, stopping orphan records.

One record in the first table can link to many in the second table. Example: one customer has many orders.

Each record in one table links to at most one record in the other. Example: one person has one passport.

Use a link (junction) table that holds two foreign keys, one for each table.

A primary key made from two or more fields used together to make a record unique.

Any field that could be the primary key because it is unique, such as an email address.

A natural key comes from real data, like a National Insurance number. A surrogate key is made by the system, like an ID.