Relational data, keys and queries

≈ 42 min

Relational data, keys and queries

A relational database stores facts in related tables. A primary key identifies one row; a foreign key records a relationship. Normalisation reduces repeated facts so that correcting a learner detail happens once instead of in every attendance or loan record.

Reasoning routine. State the information available, the rule to apply, the result required and one boundary or failure case.

Worked example. Store learner details in Learner and borrowing events in Loan. Each Loan refers to a learner ID and a book ID instead of copying names and titles into every row.

Which statement best reflects this lesson's primary and foreign keys?

Use unique keys to identify rows and foreign keys to link related records.

Use a vague rule and trust the first result.

Ignore boundary cases and hidden assumptions.

Choose a tool before stating the problem.

Write the key term for this lesson: primary and foreign keys.

A school system needs a reliable next step. Which choice is most defensible for this topic?

Create a relationship table when a learner can join many clubs and each club has many learners.

Store an unexplained guess and call it evidence.

Give every account unrestricted access.

Hide the error so the report looks complete.

A learner can repeat a definition from Relational data, keys and queries. Which next task gives stronger evidence of mastery?

Apply the idea to an unfamiliar boundary, error or decision and justify the choice.

Repeat the lesson title without using the concept.

Choose the first option before reading the scenario.

Hide an unexpected result so the answer appears tidy.