DBMS
Relationships, Relationship Sets and Degree
A relationship is an association among entities. Relationship types have a degree, may carry their own attributes, and may connect an entity type to i...
#DBMS
Database management system concepts.
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DBMS
Keys in the ER Model
A key attribute distinguishes one entity from another. Understanding super keys, candidate keys, primary keys and partial keys at design time prevents...
DBMS
Types of Attributes in the ER Model
Attributes are simple or composite, single valued or multivalued, stored or derived, and may be complex, key or null valued. Each type converts into t...
DBMS
Entities, Entity Sets and Entity Types
An entity is a distinguishable thing the database stores facts about, an entity type is its definition, and an entity set is the collection of entitie...
DBMS
Comparing Data Models and Choosing One
A single comparison of hierarchical, network, relational, object oriented, object relational and NoSQL models, plus a practical method for choosing a...
DBMS
Object Oriented and Object Relational Models
The object oriented model stores objects with identity, state and behaviour. The object relational model adds those ideas to a relational core, which...
DBMS
The Relational Model as a Data Model
The relational model stores everything in tables and connects them by matching values rather than pointers. That one decision delivers declarative que...
DBMS
Hierarchical and Network Data Models
The hierarchical model arranges records in a tree with one parent each; the network model allows many parents through a graph of sets. Both used physi...
DBMS
What a Data Model Is
A data model is the set of concepts used to describe data, relationships, semantics and constraints. Models are grouped as high level, representationa...
DBMS
Inside the DBMS: Components and How a Query Flows
A DBMS is built from a query processor, a storage manager, a transaction manager and a recovery manager. Following one query through all of them is th...
DBMS
Centralised and Distributed Databases
A centralised database keeps all data at one site; a distributed database spreads it across several. The choice changes availability, performance, com...
DBMS
Client Server Architecture and Database Servers
In client server architecture the database server owns the data and answers requests, while clients ask questions. Understanding what the server keeps...