relational Questions
3
Solved
I was only able to find the following two differences:
The relationships in an E-R model are explicitly defined, while they are implicit in a relational model.
Relational models require an interm...
Unbodied asked 3/12, 2014 at 10:4
8
Solved
Is there a way to use relational operators (<,<=,>,>=) in a switch statement?
int score = 95;
switch(score) {
case (score >= 90):
// do stuff
}
the above example (obviously) doesn't ...
Kondon asked 9/10, 2013 at 10:38
9
Why should I use document based database like CouchDB instead of using relational database.
Are there any typical kinds of applications or domains where the document based database is more suitable...
Pterosaur asked 14/1, 2009 at 0:21
3
Solved
I want to add a new column to an already existing table, but I want to give it a default value dependent on already existing data:
e.g. Each record has a start_date. Now I want to add an open_unti...
Opalina asked 1/9, 2014 at 15:33
7
Solved
Why do database guys go on about normalisation?
What is it? How does it help?
Does it apply to anything outside of databases?
Slim asked 29/10, 2008 at 13:1
3
Solved
I am studying for exams and am failing to find a solid criteria by which I can determine if the Cartesian Product x is to be used or if Natural Join |X| is to be used.
I had come up with a rough g...
Pretender asked 2/1, 2013 at 18:38
7
Solved
Does anyone use tuples in Ruby? If so, how may one implement a tuple? Ruby hashes are nice and work almost as well, but I'd really like to see something like the Tuple class in Python, where you ca...
Feleciafeledy asked 8/2, 2009 at 16:11
3
How do I represent the SQL "not exists" clause in relational algebra?
Claudclauddetta asked 17/9, 2010 at 18:47
21
Solved
When designing tables, I've developed a habit of having one column that is unique and that I make the primary key. This is achieved in three ways depending on requirements:
Identity integer ...
Millstream asked 3/12, 2008 at 15:30
1
If I have two pointer variables, a and b, what does it mean to to use the statement "a < b"? Is doing so supposed to compare the values of their memory addresses? If so, what would be the order ...
Rayshell asked 10/11, 2017 at 18:50
2
Solved
I have looked everywhere for help on this.
I'm new to all this and I'm finding it hard to understand all the documentation on it.
Say I have this XML:
<footballteams>
<team manager="Be...
Melosa asked 24/6, 2012 at 16:34
2
Solved
Relational operators such as <, >=, == are often not bidirectional. What are the correct names for the operands to these operators? An example from an non-relational operator, division, would be...
Kutenai asked 17/4, 2016 at 7:54
4
Solved
I have a cross reference table that looks like this:
id document_id subject_id
1 8 21
2 5 17
3 5 76
4 7 88
5 9 17
6 9 76
7 2 76
It matches documents to subjects. Documents can be members of more...
Forgiven asked 10/9, 2009 at 22:54
1
Solved
Pointer relational operators do not define a total order (§ 5.9 of the C++11 standard):
If two pointers p and q of the same type point to different objects that are not members of the same objec...
Electrode asked 3/6, 2015 at 10:13
4
i.e. there is a table with only 1 primary key (no composite keys). Is it 2NF by default? Assume that it is already 1NF
Mallorie asked 19/4, 2012 at 19:41
3
Solved
Can any kind soul clarify my doubts with a simple example below and identify the superkey, candidate key and primary key?
I know there are a lot of posts and websites out there explaining the diff...
Hundredth asked 1/12, 2011 at 6:20
1
Solved
I have the following database design:
I want to add a new table named Task, which would have a one-to-many relationship with a Project(Project will have one or more tasks and particular task wil...
Laporte asked 23/9, 2014 at 18:16
12
Solved
Many database systems don't allow comments or descriptions of tables and fields, so how do you go about documenting the purpose of a table/field apart from the obvious of having good naming c...
Woodford asked 9/10, 2008 at 8:23
5
Solved
Does anyone know if there is sort of an open-source Prezi tool that works with HTML5 / javascript? I'm looking for a way to set up a flow-chart diagram and then have the browser window focus ...
Coffle asked 8/6, 2011 at 19:15
3
Solved
I'm looking for material on persistent data structures that can be used to implement a relational model.
Persistence in the meaning of immutable data structures.
Anyone know of some good resource...
Pastille asked 19/11, 2008 at 21:27
18
In a brand new program where space isn't really that big a deal, is it better to delete a row or to disable a row by let's say a boolean "Disabled" and have the program just ignore it?
For example...
Stemson asked 7/12, 2008 at 3:0
1
Solved
I have two tables: Employee (ID, Name, Address) and Store(ID,Address) and I would like to record information about people who work in each store.
I thought of making a new table called Employee_Li...
Nonanonage asked 20/2, 2013 at 11:3
4
Solved
People who read C.J.Date's Introduction to Database System or books of similar level should not have problems with definition of normalization and denormalization.
However, memory is not what it u...
Epirogeny asked 30/11, 2010 at 9:15
4
Solved
I'm part of a four-man team at a growing company of over 200 users. It's time for a massive refactoring of our proprietary software, and we're very excited to build an ideal system that we know can...
Trilobite asked 5/12, 2011 at 22:43
6
I have a simpleton question on Redis. If the key to it's performance is that it's in-memory, whey can't that be done on a regular SQL db?
Warthman asked 16/3, 2011 at 17:57
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