The database-theory tag has no wiki summary.
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0answers
33 views
Where should a default setting field be?
I am creating a database to track occurrences of incidents on buses based on an existing system. Currently the drivers can set a default bus number, which is used to pre-populate the bus number on the ...
0
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1answer
54 views
Database with insert data every 2 minutes
I have a site to develop into PHP and mysql where I take, with a cron, every two minutes 10 xml from a server parse each and insert data into my database.
Well this data are simple string (maximum 10) ...
0
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1answer
28 views
Why is LRU is not suitable for joining 2 relations in DBMS
In DBMS, can someone please explain how the LRU (least recently used) buffer replacement policy acts when joining 2 relations in a database?
I have read that LRU is not efficient when joining two ...
1
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1answer
84 views
Approach for a 2,000 table migration
What might be the best approach when converting or migrating a database containing over 2,000 tables? Where would you begin to tackle such an issue? Steps to take in the first weeks of designing? ...
0
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3answers
60 views
Column partially determining accepted values of another column, should be somehow normalized?
I have a table that describes a set of properties (yes it's metadata, in this case there's a valid reason to have it in the database); among other things I tell the type of the data that can be ...
1
vote
1answer
34 views
Adding users to a list and sort by category?
I'm using SQL-Server 2012 and I would like to know how to solve this program.
So:
I want to create a page that allows admins to manage a project, and part of it, would be to add members/employees to ...
0
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2answers
47 views
Multiple instances in Oracle
I'm really confuse with the term instance and database. So, my first question is how database and Instance are related in Oracle, I mean, whether an instance is associated with one/multiple ...
1
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0answers
21 views
Closure of attributes definition clarification
A databases book I am using states [1]:
The closure of {A1, A2, ..., An} under the FD's in S is the set of attributes B such that every relation that satisfies all the FD's in set S also satisfies ...
-1
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1answer
95 views
How can I move 5 GB data from one database to another faster?
I'm using MySQL as database with Windows server. I'm having 5 GB of data in database. Now I need to change my server and the question is that how can I transfer complete 5 GB data to one mysql ...
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0answers
37 views
Examples of a database with no consistency measures that ensures consistency through schema alone
To clarify, the database can be any type RDBMS, NoSQL/BigTable. However, it must not employ any usual consistency measures such as locks, or synchronization, but the inconsistency-invincibility must ...
0
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2answers
61 views
Academic Journals and Reviews for Database Systems [closed]
I want to start reading up on the latest advances in database technology. Can anyone tell me what are the leading academic journals on the subject?
Also, I have a friend doing a PhD in another area ...
0
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0answers
66 views
In DBMS binary relationship is better than ternary
For which reasons (Features/points) binary relationship is better than ternary one in Database ER modeling? I got something by searching in website but those are not precise and meaningful!
1
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2answers
162 views
Reflexivity axiom for inferring functional dependencies
As you know there are three Armstrong's Axioms for inferring all the functional dependencies on a relational database. (X, Y and Z are set of attributes)
Reflexivity: If X ⊆ Y, then Y → X
...
2
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1answer
114 views
Deriving formulas for input/output
I'm currently enrolled in a DBS class and am having problem with an assignment. I've searched around and have been unable to understand what it is I'm meant to be doing with this derivation formula.
...
0
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0answers
32 views
what are some reasons that we move data between different environment? [closed]
We can move data using backup-copy-restore and detach/attach, right. But what are the reasons for moving these data. I'd think we move data to another environment for recovery purpose or to build data ...
0
votes
1answer
212 views
Keep total transaction in invoice application
I want to make an application called as Invoice Application with MySQL database. Now I have designed this database. Now I want to know is this database good for Invoice Application. I will use MySQL ...
1
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1answer
605 views
Planning simple CMS: How much relation?
I'm currently in the process of designing the database for a rather minimalistic Content Management System I'm working on alone. It should allow scalability while remaining speed, especially on boxes ...
-1
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2answers
125 views
Information sources for multiple hierachy trees in a single table
I need some quality sources - books, websites etc. - to educate myself about putting multiple hierarchy trees in a single table using SQL.
I'm looking for some good theoretical and practical ...
0
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1answer
128 views
Database column vs row size
I have Column A and Column B in a single table.
I need to add 1,000,000 records to this table.
I have 2 options:
Keep 2 columns and add 1,000,000 records
Add more columns and flatten out the ...
3
votes
2answers
138 views
how is synchronization maintained between different write and read database
One of my friends was asked this question in interview. Given two different databases one on which only write is done and the other on which only read is done. How does one maintain synchronization ...
2
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5answers
598 views
Does 'Cities' deserve a separate table?
I have the following Customers table:
customer_id - int
company_name - nvarchar
street - nvarchar
city - nvarchar
comments - nvarchar
The app will only be used in part of one small country ...
2
votes
1answer
276 views
Under what conditions are polymorphic associations used? What are the alternatives?
As I understand it, polymorphic relationships among tables in a database allow one table to have one foreign key that references many tables.
I have found that tags are a common application of this ...
3
votes
4answers
147 views
Complete list of possible database “objects”?
When I finished my degree in Programming and Database I remember there being a general list of database "objects" like this:
data types (a list unto itself)
fields
records
tables
views (sort of like ...
8
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4answers
307 views
What is a database?
There was lot of discussion in this question: What database technologies do big search engines use?
So much discussion that it made me confused. So... what is a database, anyway? Are only relational ...
3
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1answer
184 views
to what “scale” of applications does nosql support?
Recently i came across the Nosql database concept, though i learnt how to and why of it, i did not get a proper answer to the question , to what scale of project does it support?
Will it support ...
2
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1answer
205 views
Postgres synchronized backup - what's with the archive?
I am setting up a Postgres 9.1 master and a hot standby-server. I read the documentation but I'm not quite sure yet what I should do with my WAL files.
Every commit is done on both servers before ...
3
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2answers
515 views
Ready-to-Use Database models example
Where can I find ready-to-use database models ?
I don't need a database with data in it, but only schemas (UML diagrams). Perhaps something like the data models at this link, but much more complex ...
1
vote
1answer
156 views
Is an anomaly free relation necessarily normalized?
A normalized relation can still suffer anomalies. Going the other way, which (if any) normal forms can be violated by a relation that's free from anomalies? If such exist,
For each such normal form ...
0
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3answers
325 views
SQL Server : primary keys advice to my whitepaper needed
I've tired to explain to every new junior developer in our r&d team why he should use Primary Keys and how to do that. So I decided to write small whitepaper, which every new developer should ...
1
vote
1answer
89 views
Overlapping Transactions
Apolgies in advance if this has been discussed before, or is even fundamental enough for it to be outlined on, say, Wikipedia. I just felt that asking would be more efficient!
Anyway, I want to ask ...
4
votes
3answers
908 views
Why are NULLs sorted first?
Why is it that when we have a NULL value in a column and we order by the value ascending, the NULLs are sorted first?
select 1 as test
union all
select 2
union all
select NULL
union all
select 3
...
7
votes
1answer
480 views
Is DB Normalization done purely based on the primary key or is it done based on all the candidate keys?
I have come across two flavours of the normalization procedure while referring the internet and textbooks. viz.
Type 1. Normal forms based only on the primary key.
In this type,
-> 2NF disallows ...
4
votes
2answers
486 views
Right Full Outer Join Query
I came across 1 query which is
Select * from R Natural Outer Join S
Where R=(A,B) has tuples {(1,2),(1,2),(3,4)} and S=(B,C) has tuples {(2,5),(2,5),(4,6),(7,10)}.
To implement this I created 2 ...
2
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2answers
686 views
Does the SELECT statement count into DML?
Looking at the name Data Manipulation Language (DML) I would assume, that all contained statements are actually for manipulating data.
As far as I know the SELECT statement can only be used to query ...
33
votes
5answers
6k views
When to use TINYINT over INT?
In general, I always use Ints. I know that in theory this is not the best practice, though, since you should use the smallest data type that will be guaranteed to store the data.
For example, it's ...
2
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1answer
319 views
Transaction and data consistency during a failure
When a database begins a transaction, all statements executed in that transaction are isolated and atomic (and consistent and durable). These are pretty much the definition of a transaction.
...
16
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1answer
501 views
What is the reasoning behind the CAP theorem?
http://en.wikipedia.org/wiki/CAP_theorem
http://www.cs.berkeley.edu/~brewer/cs262b-2004/PODC-keynote.pdf
I think it is not very straightforward why only two of
Consistency
Availability
Partition ...
9
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8answers
339 views
Pioneers in Database Research
Who all people have made life changing contributions to database research? I want to know more about them.
