Technical Interview Questions and Answers :: Sopra Steria
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Unlike Relational systems in System R
> Domains are not supported
> Enforcement of candidate key uniqueness is optional
> Enforcement of entity integrity is optional
> Referential integrity is not enforced
A collection of conceptual tools for describing data, data relationships data semantics and constraints.
This data model is based on the real world that consists of basic objects called entities and of a relationship among these objects. Entities are described in a database by a set of attributes.
This model is based on a collection of objects. An object contains values stored in instance variables within the object. An object also contains bodies of code that operate on the object. These bodies of code are called methods. Objects that contain same types of values and the same methods are grouped together into classes.
A database schema is specified by a set of definitions expressed by a special language called DDL.
It executes low-level instruction generated by compiler.
The domain of an attribute must include only atomic (simple, indivisible) values.
It is based on the concept of full functional dependency. A functional dependency X -> Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.
A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.