Information Systems and Databases
What you must know
An information system collects, stores, processes and outputs data to support decisions. Learn database structure: tables, records, fields, primary and foreign keys, and relationships (one-to-one, one-to-many, many-to-many). Understand flat file vs relational databases, data validation and verification, and basic SQL (SELECT, FROM, WHERE). Know the difference between data, information and knowledge, and the idea of data quality (accuracy, completeness, timeliness).
Traps candidates fall into
- Confusing validation (sensible data, e.g. range check) with verification (correct entry, e.g. double entry).
- Using a non-unique field as a primary key - keys must be unique.
- Forgetting a foreign key links to a primary key in another table.
- Describing a flat file as relational - it has no linked tables, causing repetition.
- Reversing the order of SQL clauses.
Rule of thumb
Validation checks the data is reasonable; verification checks it was entered correctly. Both are needed for reliable information.
Worked example
A library database has a Books table (BookID primary key) and a Loans table (LoanID primary key, BookID foreign key). To find overdue loans: SELECT * FROM Loans WHERE DueDate < today. The foreign key links each loan to its book without repeating book details.