Database Concepts
Key Terms
Data Integrity
The accuracy and consistency of data throughout its lifecycle. Ensured through:
- Validation rules (data type, range, format)
- Referential integrity (relationships between tables)
- Entity integrity (unique primary keys)
Data Redundancy
Unnecessary duplication of data. Problems include:
- Wasted storage space
- Inconsistency when updating
- Increased maintenance effort
Common Mistake: Confusing integrity (correctness) with redundancy (duplication)
Single-Table Database
A database with one table containing all data.
Example: Students Table
| StudentID | Name | YearLevel | |
|---|---|---|---|
| 1001 | A. Singh | 12 | asingh@school.edu |
| 1002 | L. Chen | 12 | lchen@school.edu |
Database Objects
- Tables - Store the data in rows and columns
- Forms - User interface for data entry
- Queries - Extract and filter specific data
- Reports - Formatted output for printing/sharing
Primary Key
A field that uniquely identifies each record. Must be:
- Unique - no duplicates
- Not null - cannot be empty
- Unchanging - shouldn't need to be modified