Database Concepts — common mistakes

Examiners frequently ask about resolving a many-to-many relationship. Remember the rule: you must create a new 'linking' table in between the two original tables. This linking table will contain foreign keys from both original tables, which together will often form a composite primary key.

A spreadsheet (like Excel) is primarily a calculation tool that stores data in a single flat file. A database is designed for storing, managing, and querying large amounts of related data across multiple tables. Databases offer far greater data integrity, security, scalability, and control over relationships between data.

If you tried, you'd have to put multiple values in a single field (e.g., a list of CourseIDs in the Student table), which violates the principles of relational database design (first normal form). This makes querying and maintaining data extremely difficult and inefficient. A linking table provides a clean, structured way to represent each individual student-course connection as a unique record.

No, this is a common misconception. The database is the collection of data itself (the files on the disk). The DBMS is the software you use to manage and interact with that data (e.g., MySQL, Microsoft Access, Oracle). Think of it like this: your MP3 files are the 'database' of music, and Spotify or iTunes is the 'DBMS' you use to play and organise them.

A candidate key is any field (or combination of fields) that could potentially be used as the primary key for a table because it uniquely identifies each record. A table might have several candidate keys. The database designer then chooses one of these candidate keys to be the official primary key.