DDMA Level II
Database cheat sheet
Every chapter's key points, formulas and definitions on one page, for the last week before the exam. Each heading links to the chapter that explains it.
Database concepts
- A database is an organised, persistent collection of related data, and a DBMS is the software that creates, manages and controls access to it, for example MySQL, PostgreSQL or Oracle Database.
- Relation, tuple and attribute are the formal names for table, row and column; degree counts a relation's attributes and cardinality counts the tuples it currently holds.
- The database approach controls and shares data centrally, minimises redundancy and lets the DBMS enforce consistency and integrity rules on every access.
- Databases may be centralized, distributed, relational, cloud, hierarchical (each record has one parent) or network (a record can have several parents).
- The DBMS environment has four components: hardware, software, data and procedures.
Key terms
- Data
- Raw, unprocessed facts with no context on their own.
- Database
- An organised, persistent collection of related data.
- Database Management System (DBMS)
- Software that creates, manages and controls access to a database; MySQL, PostgreSQL and Oracle Database are all examples.
- Relation
- The formal term for a table.
- Tuple
- A single row within a relation, one record.
- Attribute
- A single column within a relation, one field.
- Degree
- The number of attributes (columns) a relation has.
- Cardinality
- The number of tuples (rows) a relation currently holds.
- Centralized database
- All data stored and managed at a single physical location.
- Distributed database
- Data spread across multiple physical locations, appearing as one logical database.
- Relational database
- Organises data into related tables linked by keys, the dominant model this paper focuses on.
- Cloud database
- Runs on a cloud provider's infrastructure, accessed over the internet.
- Hierarchical database
- Organises data in a tree structure, each record has one parent.
- Network database
- A more flexible variant of hierarchical, where a record can have multiple parents.
- Hardware
- The physical computer and storage the database runs on.
- Software
- The DBMS itself, plus the operating system it runs under.
- Procedures
- The documented instructions for using and administering the database.
The rest of the sheet covers
- Relational database design
- Structured Query Language
- Database performance
- Exam technique and revision
- Glossary