Cheat sheet · Class 12 · CBSE · Science Computer Science
Database Management System cheat sheet
The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.
CBSE Class 12 · Computer Science
Cheat sheet
Chapter 1Database Management System
Relation = table, tuple = row, attribute = column.
1. Why a DBMS?
- File systems suffer from redundancy, inconsistency, poor access control and data dependence.
- DBMS: MySQL, Oracle, PostgreSQL, SQLite.
2. Relational Model Terms
| Term | Meaning |
|---|---|
| Relation | table |
| Tuple | row (record) |
| Attribute | column (field) |
| Domain | set of allowed values |
| Degree | number of attributes |
| Cardinality | number of tuples |
3. Keys
| Key | Role |
|---|---|
| Candidate | can uniquely identify a tuple |
| Primary | chosen candidate key (unique, not NULL) |
| Alternate | candidate keys not chosen |
| Composite | key made of 2+ attributes |
| Foreign | refers to the primary key of another table |
4. Key Points
- Schema: structure; instance: data at a moment.
- Metadata: data about data (data dictionary).
- Referential integrity via foreign keys.
- Order of rows/columns doesn't matter.
Remember: Relation terms | degree & cardinality | 5 keys
Database Management System: questions and notes
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