Define the five basic operators of relational algebra, Database Management System

Assignment Help:

Define the five basic operators of relational algebra?

Five basic operators of relational algebra are:
1. Union (∪∪∪∪) - Selects tuples which are in either P or Q or in both of them. The duplicate tuples are eliminated.
R = P ∪ Q
2. Minus (-) - Removes generally common tuples from the first relation.
R = P - Q
3. Cartesian Product or Cross Product (××××) - The cartesian product of two relations is the concatenation of tuples belonging to the two relations and consisting of all probable combination of the tuples.
R = P × Q
4. Projection (ππππ) - The projection of a relation is described as a projection of all its tuples over a few set of attributes, i.e., it yields a vertical subset of the relation. It is used to either decrease the number of attributes (degree) in the resultant relation or to reorder attributes. The projection of a relation T on the attribute A is denoted through πA(T).
5. Selection (σσσσ) - Selects only some of the tuples, those satisfy given criteria, from the relation. It yields a horizontal subset of a given relation, i.e., the action is defined over a complete set of attribute names but just a subset of the tuples are involved in the result.
R = σB(P)

 


Related Discussions:- Define the five basic operators of relational algebra

Explain data independence, Explain data independence ? Data independenc...

Explain data independence ? Data independence is the capacity to modify the schema at one stage of a database system without having to change the schema at the further level.

How many types of views are there, How many types of Views are there? ...

How many types of Views are there? There are Four types of views:- Database View Help View Projection View Maintenance View

What are the dbms languages, What are the DBMS languages? Explain.  Ans...

What are the DBMS languages? Explain.  Ans: a) Data Definition Languages (DDL): It is employed to specify database schema for example CREATE DROP statements etc.     b)  Dat

Er schema, Consider entity type Employee with attributes empNumber (this is...

Consider entity type Employee with attributes empNumber (this is unique), empName, and the year when he/she was hired. An employee can either be a technical employee, a marketing e

Replicating data, Replicating Data One approach that may support effici...

Replicating Data One approach that may support efficient access to dissimilar applications as above may be to give access to every of the applications from dissimilar replicate

List the requirements needed to design a trigger, List the requirements nee...

List the requirements needed to design a trigger. The requirements are:- Specifying when a trigger is to be implemented. State the actions to be taken when the trigger im

Text mining, Text Processing: Use readLines to read SOU.txt into R. Cr...

Text Processing: Use readLines to read SOU.txt into R. Create a vector called Pres containing the names of the presidents giving each speech. To do this, rst identify the lin

Define the terms physical schema and logical schema., Define the terms 1) p...

Define the terms 1) physical schema 2) logical schema. Physical schema: The physical schema explains the database design at the physical level, which is the lowest level of abs

What is thread splitting, What is Thread splitting A thread of cont...

What is Thread splitting A thread of control is a path by which a set of state diagrams on that a single object is active at a time. Objects are shared between threads

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd