cardinality Questions
19
Solved
Is it possible to determine the cardinality of a c++ enum class:
enum class Example { A, B, C, D, E };
I tried to use sizeof, however, it returns the size of an enum element.
sizeof(Example); /...
Subcartilaginous asked 20/2, 2013 at 20:27
2
Solved
LowCardinality fields in ClickHouse are an optimization where the values are dictionary-encoded for faster lookups and smaller storage. As per documentation:
The efficiency of using LowCarditali...
Insanitary asked 11/6, 2020 at 15:30
4
Solved
I thought that generally speaking using %>% wouldn't have a noticeable effect on speed. But in this case it runs 4x slower.
library(dplyr)
library(microbenchmark)
set.seed(0)
dummy_data <-...
Daglock asked 11/3, 2016 at 5:55
5
From my understanding you don't gain much by setting an index in a column that will hold few distinct values.
I have a column that holds a boolean value (actually it's a small int, but I'm using it...
Bateau asked 21/1, 2010 at 21:46
4
Solved
My school book Database Systems defines cardinality as follows:
The cardinality of a relation is the number of tuples it contains. By contrast, the number of tuples is called the cardinality of ...
Elston asked 28/8, 2014 at 11:47
3
The function below takes two BitSets, makes a copy of the first (it must not be overridden), intersects the copy with the second (bitwise AND) and returns the cardinality of the result.
public int...
Aedes asked 2/8, 2015 at 12:55
0
How can I generate cardinal numbers(One, Two, Three) using NumberFormatter in Swift using Locale settings.
For example, I am able to convert 1 minute -> One minute using English Locale setting...
Lydie asked 4/1, 2018 at 12:0
6
Solved
Could somebody explain to me, with the help of examples, what is cardinality in databases?
Funchal asked 16/5, 2012 at 14:49
6
Solved
I am having a hard time understanding what is the difference between the Max and Min cardinalities when trying to design a database.
Secluded asked 24/2, 2011 at 12:0
1
Solved
I keep coming across these terms: high cardinality and low cardinality in Cassandra.
I don't understand what exactly they mean. what effects they have on queries and what is preferred.
Please expl...
Gustafsson asked 3/8, 2014 at 2:49
1
Solved
I am studying Database Development and I am at the stage where I have to create my own ER Models. Everything is fine so far with StarUML however the course notes don't mention how to add muliplicit...
Toplevel asked 1/11, 2012 at 18:55
1
Solved
What's the difference between the operator * and the operator 0..* in UML (unified modeling language)?
I saw this two cardinality operators, but I don't now which one I must to use.
Anglesite asked 1/9, 2013 at 18:17
3
Solved
I would like to know once and for all how to write UML cardinalities, since I very often had to debate about them (so proofs and sources are very welcome :)
If I want to explain that a Mother ca...
Guthrun asked 18/7, 2013 at 13:45
1
Not a long ago I started to optimize queries for mysql db. I created some indexes and decided to see their params, using show index from syntax. And saw that cardinality doesn't equal distinct coun...
Senegambia asked 24/5, 2013 at 10:34
2
Solved
So, I've read a whole lot of answers here on stackoverflow, but I'm still confused about the whole concept thereof. Specifically, I've gone over this article (including all the ones it references),...
Tripartite asked 16/3, 2013 at 0:18
2
Solved
I have a schema with a parent-child relationship between two entities. It's a one-to-many, so would naturally be implemented as:
table Parents
id
table Children
id
parent_id
However, I also ...
Rosariarosario asked 3/1, 2013 at 9:1
3
Solved
I'm trying to find a better way in expressing my cucumbers so I am looking for an ordinal to cardinal function that converts this:
When I fill up the first passenger field
Then I should see the pa...
Caveman asked 6/5, 2011 at 5:20
4
As answered in this question: Cardinality in PostgreSQL, cardinality is enfforced using constraints.
Cardinality rules define the allowable counts of the relationships – one-to-many, many-to-many,...
Overhaul asked 12/2, 2012 at 14:46
2
Solved
I have been playing at work with some very very large sets of data, typically several billions of elements, that are all maintained in a memcached cloud and periodically dumped into files, and for ...
Canonicity asked 15/4, 2012 at 18:1
2
Solved
I have database tables that look like this:
A Task can be mapped to a Module, or not mapped at all (0...1). I'm using Entity Framework database-first, and when I generated the model from the dat...
Gamaliel asked 11/4, 2012 at 15:31
2
I'm having performance problems on the live version of a system which I can't reproduce locally.
In comparing a few EXPLAIN results on my local copies of the database with the live one, I note th...
Corbin asked 29/6, 2011 at 13:46
1
Solved
We have a massive table where I need to make an update on a single row. I don't know the primary key of the row, but I have a varchar value that is unique within that table. I also have the value o...
Masaccio asked 30/6, 2011 at 15:25
1
Solved
I have a UML diagram of what I need my database schema to look like. This diagram includes roles and cardinality. How can I enforce cardinality in Postgres?
Tenpin asked 28/6, 2010 at 18:44
1
Solved
Say you have a MySQL 5.0 MyISAM table with 100 million rows, with one index (other than primary key) on two integer columns.
From my admittedly poor understanding of B-tree structure, I believe th...
Perrin asked 8/4, 2010 at 2:23
2
I have added a FULLTEXT index to one of my MySQL database tables as follows:
ALTER TABLE members ADD FULLTEXT(about,fname,lname,job_title);
The problem is that using phpmyadmin I can see the car...
Tungus asked 16/4, 2009 at 10:43
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