Join operation, Database Management System

The JOIN operation is applied on two relations. When we want to choose related tuples from two given relation join is used. The join operation need that both the joined relations must have at least single domain compatible attributes.

Syntax:

R1 R2 is used to join related tuples from two relations R1 and R2 into a single tuple.

is of the form:

ANDAND..............AND.

  • Degree of Relation:

Degree (R1   R2) <= Degree (R1) + Degree (R2).

  • There are three types of joins:

a)   Theta join

When every condition is of the form A θ B, A is an attribute of R1 and B is an attribute of R2 and have the similar domain, and θ is one of the comparison operators { ≤, ≥, ≠, =, <, <}.

Posted Date: 3/6/2013 5:53:13 AM | Location : United States







Related Discussions:- Join operation, Assignment Help, Ask Question on Join operation, Get Answer, Expert's Help, Join operation Discussions

Write discussion on Join operation
Your posts are moderated
Related Questions
The need for three level architecture The aim of the three level architecture is to divide each user's view of the database from the way the database is physically shown.

1) Define a job scheduling strategy that will meet business requirement of reporting availability by 6am CST for the following cubes? Show the job scheduling dependencies in a pict

What does the cardinality ratio specify? Mapping cardinalities or cardinality ratios state the number of entities to which another entity can be associated. Mapping cardinaliti

Implementation of association as an object Implement as a separate association object, independent of either class, as in Figure. An association object is a group of pairs

Briefly explain each of the following database terms. Use no more than 2-3 lines for each term. 1. DBMS 2. Update Anomaly 3. Alias (referring to tables in SQL queries)


How does a query tree represent a relational algebra expression?  Discuss any three rules for query optimisation, giving example as to when should each rule be applied.     Ans

Q. Describe how an ER schema can be represented by relation schemas and constraints arising from ER design can be mapped to constraints on a relation schema.     The entity rela

Decompose the table with the following description and functional dependencies into a set of equivalent tables normalized to 3NF or BCNF. This database stores records from a (ve

A domain is a set of permissible values that can be given to an attribute. So each attribute in a table has a definite domain. Values to these attributes cannot be assigned outside