Database Concepts and Data Management
Database Concepts and Data Management tests relational terminology, keys, basic SQL and the purpose of DBMS objects. You should be able to identify fields and records, explain primary and foreign keys, and read a simple SELECT statement.
Core rules and concepts
- A table stores rows (records) and columns (fields). A primary key uniquely identifies each record and cannot be null or duplicated.
- A foreign key refers to a primary key in another table, creating a relationship and supporting referential integrity.
- A DBMS stores, retrieves, updates and secures data. Queries request data; forms support data entry; reports present output.
- SQL SELECT retrieves columns. WHERE filters rows; ORDER BY sorts results. Text values in SQL are usually enclosed in single quotes.
- Normalisation reduces duplication and update anomalies by organising data into related tables.
Worked example
Students(StudentID, Name, Class) and Marks(StudentID, Subject, Score) are related. StudentID is the primary key in Students and a foreign key in Marks. To list names of Class 10 students, use: SELECT Name FROM Students WHERE Class = '10'; Reasoning: SELECT chooses the column, FROM names the table, and WHERE filters records. The foreign key in Marks allows each student to have several subject scores without repeating the student name in every row.
Traps that cost marks
- Treating NULL as zero or as an empty string; NULL means unknown or not applicable.
- Duplicating a primary-key value or leaving it blank.
- Deleting a parent record still referenced by a foreign key without handling the relationship.
- Writing numeric filters with quotes when the column is numeric, or omitting quotes for text.