AQA GCSE · Question 18.3 · Relational databases and structured query language (SQL)
State the name of the field from the Member table that is the most suitable to use as the primary key.
How to approach this question
A primary key must be a field that uniquely identifies each record in the table. Look at the fields in the `Member` table: `MemberID`, `FirstName`, `LastName`, `DateJoined`. Which of these is guaranteed to be unique for every single member?
Full Answer
A **primary key** is a field in a table that uniquely identifies each record. It must have a unique value for each row and cannot be null.
Looking at the `Member` table fields:
- `FirstName`: Not unique (two people could be named Peter).
- `LastName`: Not unique (two people could have the last name Hill).
- `DateJoined`: Not unique (Zarah and Penny joined on the same day).
- `MemberID`: This field contains a unique number for each member (1, 2, 3, 4). It is specifically designed to be a unique identifier.
Therefore, `MemberID` is the most suitable primary key.
Common mistakes
✗ Choosing a field that is not guaranteed to be unique, like `FirstName` or `LastName`.
✗ Naming a field from the wrong table (e.g., `AwardID`).
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