Define union compatibility, Database Management System

Assignment Help:

Define union compatibility? Explain why INTERSECTION of two relations cannot be performed if they are not union compatible?

Two relations R(A1, A2,-------, An) and S(B1, B2,-----, Bn) are said t union compatible if they have the similar degree n and if dom (A) = dom(B) for all i=1---ni i Intersection needs two relations to be union compatible since or else it is not probable to formulate the criterion as to on what basis will attributes be considered as general.


Related Discussions:- Define union compatibility

What is a hashing function, What is a hashing function?  What are the prope...

What is a hashing function?  What are the properties of a good hashing function?  Describe the folding technique for hashing functions.      Ans:  Hashing function is a method

Relational operations, Let us now talk about the relational operations: ...

Let us now talk about the relational operations: SELECT The select operation is used to select few specific record from the database based on different criteria, This is a un

Equijoin, When every condition appears with equality condition (=) only. c)...

When every condition appears with equality condition (=) only. c)   Natural join (denoted by R*S) When two join attributes have the similar name in both relations. (Tha

What is the use of sub queries, What is the use of sub queries? A sub q...

What is the use of sub queries? A sub query is a select-from-where expression that is nested with in another query. A common use of sub queries is to do tests for set membershi

Timestamp type, Do NOT use the timestamp type.  Use separate date and time ...

Do NOT use the timestamp type.  Use separate date and time data types only.  Figure out how to define an SQL insert statement that uses built-in SQL (or MySQL) functions to define

What are the properties in a relation, What are the properties in a relatio...

What are the properties in a relation ? In a relation Ordering of rows is immaterial and No two rows are identical.

State about the advance object design, ADVANCE OBJECT DESIGN Introduct...

ADVANCE OBJECT DESIGN Introduction Analysis is the initial step of the OMT methodology. It is apprehensive with devising a precise, concise, correct and understandable mo

Higher normal forms, Higher Normal Forms Is there more normal forms beyond...

Higher Normal Forms Is there more normal forms beyond BCNF? Yes, though, these normal forms are not based on the concept of functional dependence. More normalisation is needed if

Read-set(t) and timestamps-optimistic concurrency contents, read-set(T) : E...

read-set(T) : Each data items that are read by a transaction T Timestamps : for all transaction T, the start-time and the end time are reserved for all the three phases.

Describe the host language, Describe the host language? Host Language:...

Describe the host language? Host Language: You could write applications along with SQL statements embedded inside a host language. The SQL statements give the database inter

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