Solved

I have a question according to the relational model database

Posted on 2011-03-23
5
613 Views
Last Modified: 2013-11-15
In terms of the relations shown below, what is the appearance of the realtion RESULT after executing each of thesre instructions:
X relation                          Y relation
U V W     RS                                
A Z 5                                3 J
B D 3                                4 K
C Q 5

RESULT <- PROJECT W from X
0
Comment
Question by:antatiana
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
5 Comments
 
LVL 18

Accepted Solution

by:
BigSchmuh earned 333 total points
ID: 35205287
Projection is an operation to retrieve some of the relation values.
Project W From X should lead you to get the W column as a result.
...and please try to get your homework done by yourself, as you obviously should have this "Projection" information in some reference books...
0
 
LVL 33

Assisted Solution

by:ste5an
ste5an earned 167 total points
ID: 35205466
hi,

BigSchmuh is right. Simply read the basic theory:

http://en.wikipedia.org/wiki/Relational_Database#Relational_operations

"The projection operation extracts only the specified attributes from a tuple or set of tuples."
0
 

Author Comment

by:antatiana
ID: 35232465
thanks. Of course I am doing my homework myself always and this homework was made by ,yself too!!!:) It's just attemp how site is working as I am new here. Of course in all other my quetsions I will follow main rules and if I'd like to ask something from experts according my homework I will do it just in special events if some qeustions are are really very contradictory, I have doubts and I reallyneedhelp of experts to solve my problem.
0
 
LVL 18

Assisted Solution

by:BigSchmuh
BigSchmuh earned 333 total points
ID: 35232932
One must pay the price for asking EEE to spend their time on topics...
0

Featured Post

Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
T-SQL: Do I need CLUSTERED here? 13 64
Is Dropbox the only way to upload large files? 3 53
Very Large data in MYSQL 7 95
Access table not showing correct column 6 25
Read about achieving the basic levels of HRIS security in the workplace.
When table data gets too large to manage or queries take too long to execute the solution is often to buy bigger hardware or assign more CPUs and memory resources to the machine to solve the problem. However, the best, cheapest and most effective so…
Video by: Steve
Using examples as well as descriptions, step through each of the common simple join types, explaining differences in syntax, differences in expected outputs and showing how the queries run along with the actual outputs based upon a simple set of dem…
Polish reports in Access so they look terrific. Take yourself to another level. Equations, Back Color, Alternate Back Color. Write easy VBA Code. Tighten space to use less pages. Launch report from a menu, considering criteria only when it is filled…

730 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question