What is Domain-Key Normal Form?
A relation is said to be in DKNF if all constraints and dependencies that should hold on the the constraint can be enforced by simply enforcing the domain constraint... Read more »
Archive for June, 2006
What is Fully Functional dependency?
It is based on 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... Read more »
How does Tuple-oriented relational calculus differ from domain-oriented relational calculus?
The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL The domain-oriented calculus... Read more »
What is System R?
System R was designed and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its purpose was to demonstrate that it is possible... Read more »
Define the “integrity rules” .
There are two Integrity rules. Ø Entity Integrity: States that “Primary key cannot have NULL value” Ø Referential Integrity: States that “Foreign Key can... Read more »
What are levels of Abstraction?
The are three levels of abstraction: Ø Physical level: The lowest level of abstraction describes how data are stored. Ø Logical level: The next higher level of... Read more »
DBMS V/s File Processing System
DBMS Ø Redundancy is controlled. Ø Unauthorised access is restricted. Ø Providing multiple user interfaces. Ø Enforcing integrity constraints. Ø Providing backup... Read more »
What are OPTIMIZER HINTS ?
Specifies a hint string that Oracle Forms passes on to the RDBMS optimizer when constructing queries. Using the optimizer can improve the performance of database... Read more »
Explain the Memory Structures of the Oracle database ?
Oracle creates and uses memeory sructures to complete several jobs. For example, memory is used to store program code being executed and data that is shared among... Read more »
What are Extents?
The next level of logical database space is called an extent. An extent is a specific number of contiguous data blocks, obtained in a single allocation, used to... Read more »
What are Hash clusters ?
Hash clusters are also cluster table data in a manner similar to normal clusters. However, a row is stored in a hash cluster based on the result of applying a hash... Read more »
What are Packages ?
A PACKAGE is a PL/SQL object that groups PL/SQL types, variables, SQL cursors, exceptions,procedures, and functions.Each package has a specification and a body.... Read more »
What is a SEGMENT ?
A SEGMENT is another way to classify the space allocated to a table, index, or cluster. A table has one segment that consists of all of its extents. Every index... Read more »
What are CLUSTERS ?
A CLUSTER is a means of storing together data from multiple tables, when the data in those tables contains information and is likely to be accessed concurrently. Read more »
What are the different types of SQL commands ?
DDL ( Data definition language ) DML ( Data manipulation language ) TCL ( Transact control language) Session Control Statements. ( ALTER SESSION, ROLE ) System... Read more »