Questions tagged [relational]
526 questions
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votes
2 answers
Projection of 2 tables in Relational Algebra
Considering these 2 tables:
Cd (cd_id, title, no_tracks, date, position, weeks)
Band (band_id, band_name)
The task is: List all the band names and cd titles in Relational Algebra.
I wrote it this way: Π band_name (Band) AND Π title (Cd), however…
Charles David
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votes
2 answers
Need guidance on SQL query
So the problem is:
fan(fanID: integer, fanName: string)
band(bandID: integer, bandName: string)
likes(fanID: integer, bandID: integer)
bandMember(memID: integer, memName: string, bandID: integer, nationality: string)
(a) List the names of the bands…
david
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votes
1 answer
Database design decision translating requirements to relational models
So I've volunteer to create a Registering system for my local church's education ministry. It should be able to register new students and keep track of their progress. Here are the requirements I've managed to gather:
The educational institution…
ecr
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votes
1 answer
Diff in days(month / year) - Laravel
The question is how is it possible to get difference in days from before to today and knowing this difference is happened in the past?
Mahdi Rashidi
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votes
1 answer
Sequence of or and and in if block not working correctly
CCMT c = new CCMT();
c.ccd = null;
Optional cType = Optional.ofNullable(ccmtRequest).map(CCMT::getCcd).map(MOEH::getDestCtry);
System.out.println(cType.isPresent()); // false
if(cType.isPresent() &&…
tusharRawat
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- 24
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votes
1 answer
Database Design: When should I use multiple database?
Background:
I'm trying to build the backend services of an app. This app has rooms where a user can join in to. When a user joins a room, s/he can exchange some data with other users through socket. Outside of the room, the user can view the…
asdf04
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-2
votes
1 answer
Determine if a measure is aggregable or not in data-warehouse
Can someone please tell me a 'general use', step-by-step method to find out what are the non-aggregability fields in a datamart. Here an example I found:
Notes: italic means 'key', bold identifies 'shortenings', 'column' is an alias for…
DDS
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votes
1 answer
i have univarsity sechema as mention following and now i want to add new table but it shows erroe? help me
//University DDL statements
create table classroom
(building varchar(15),
room_number varchar(7),
capacity numeric(4,0),
primary key (building, room_number)
);
create table department
(dept_name …
Onkar Marbhal
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-2
votes
1 answer
Do I have too many columns in my MySQL table?
I'm a junior doctor and I'm creating a database system for my senior doctor.
Basically, my senior Dr wants to be able to store a whole lot of information on each of his patients in a relational database so that later, he can very easily and quickly…
Cheerag Patel
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votes
1 answer
Best Relational Database Diagrams
I am looking for good-designed and real life relational database diagrams. Could you offer any book or other sources? I prefer books.
Thank you.
akadal
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votes
1 answer
Database relational schema
I'm working for a database project that my professor gave to me and now i'm designing the relational schema of database.
I have three entity types album, photo and video that means an album can contain both of them, but I have no idea how to tie…
ilir.beqiri
- 11
- 1
-2
votes
1 answer
Retrieve data in combobox from SQL Server in VB.NET
I have a database column, Province=(Punjab, Sindh, Blochistan, Sarhad) and other database table City=Fsd, Lahore, Multan, etc, and I have another database table city=Chiniot, Khushab, Tando, Adam, Khan, etc. Also another two more columns of city…
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votes
2 answers
Relational algebra operations
I'm stuck with relational algebra.
I mean, how can I express functions like "SUM(), COUNT()," etc in RA?
Thanks, any help will be kindly appreciated
ubi_v
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votes
3 answers
is there a simpler way to do: if(num1 > num2 && num1 > num3), for bigger list of variables to compare?
I'd like to know (just for knowing) if there is a way to execute the following instructions with simpler code: (C++)
if(a > b && a > c && a > d)
is it possible to replace it with something like this:
if(a > b, c, d)
YaRmgl
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votes
3 answers
Relational operator in C while using real variables
Why the output is not as expected?
#include
void main(){
float a,b,c;
b=0.7;
if( b<0.7 )
printf(" It should NOT be here");
else
printf("It Should be here");
}
Krishnajyoti Das
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