04. Database foundations, keys and integrity - revision mindmap
All mindmaps · Full chapter · Practice answers
Open full-resolution image · Printable collection - page 4
The map is a completed revision summary. Cover a branch and reconstruct it, then try the linked chapter practice. Read the image at full size when labels are small.
Text version
Database model
- Database versus DBMS
- Table/relation, row/record/tuple, field/attribute
- Domain: permitted values; schema versus current data
- DBMS benefits and costs; data independence
Choosing identifiers
- Candidate: unique and minimal
- Primary: chosen candidate, unique and non-null
- Composite: several attributes
- School secondary/alternate: unchosen candidate
Linking tables
- Foreign key → referenced key
- Entity integrity versus referential integrity
- Repeated foreign keys can represent legitimate relationships
- Null only where permitted; do not infer uniqueness from sample rows
Redundancy and inconsistency
- Same descriptive fact stored repeatedly
- Update anomaly: conflicting copies
- Insertion anomaly: cannot record one fact independently
- Deletion anomaly: removing a row loses another needed fact
Transactions and data care
- Atomicity: all-or-nothing change
- Consistency: defined integrity rules
- Isolation: controlled concurrent interaction
- Durability: committed change survives failure; backup versus archive
Worked example & exam traps
- Student(StudentID PK); Course(CourseID PK).
- Enrolment(StudentID FK, CourseID FK): pair can be its PK.
- One student on two courses repeats a valid FK, not a duplicate enrolment.
- Avoid: repeated value always redundant; foreign key always unique
Sources and reading
This map condenses Chapter 04 and its source trail. Use the self-learning reading guide for the corresponding VJC pages and A notes. It does not add topics to the stated promo scope.