Data Management and Database Basics
What this domain tests
The vocabulary of databases, why a DBMS beats a stack of files, and simple query and validation logic.
Core concepts
- Hierarchy: character → field (column/attribute) → record (row/tuple) → table (relation) → database.
- Primary key uniquely identifies each record and cannot be null; foreign key is a field in one table that refers to the primary key of another, creating the relationship.
- A DBMS controls redundancy, enforces integrity, allows concurrent access, provides backup/recovery and security.
- Data types matter: text, number, date, currency, yes/no. A phone number is usually stored as text so the leading zero survives.
- Validation vs verification: validation checks acceptability (range, format, presence, list); verification checks that the data was copied correctly.
- Basic SQL: SELECT columns FROM table WHERE condition; INSERT, UPDATE, DELETE.
Worked example
A school keeps a Student table (Roll_No primary key, Name, Class) and a Marks table (Roll_No, Subject, Marks). Reasoning: Roll_No in Marks is a foreign key pointing to Student. To list names and marks: SELECT Student.Name, Marks.Marks FROM Student, Marks WHERE Student.Roll_No = Marks.Roll_No. The join condition is what prevents every student being paired with every mark.
Traps that cost marks
- Naming a field that repeats values (Class) as the primary key.
- Confusing primary key with foreign key.
- Writing SELECT * with no WHERE when a condition was specified.
- Calling a spreadsheet a DBMS without mentioning relationships, integrity and controlled redundancy.