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What are database normal forms and can you give examples? [closed]
...piece of information, and there can be no duplicate rows.
2NF and 3NF are all about being dependent on the primary key. Recall that a primary key can be made up of multiple columns. As Chris said in his response:
The data depends on the key [1NF], the whole key [2NF] and nothing but the key [3NF] ...
How can I randomize the lines in a file using standard tools on Red Hat Linux?
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I'm usually a Perl fan, but came across this ruby example which has the benefit of being shorter: ruby -e 'puts STDIN.readlines.shuffle'. It would need testing on big inputs to see if the speed is comparable. (also works on OS X)
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Why 0 is true but false is 1 in the shell?
The above will output 1 , which is contradictory with all other programming languages I know.
10 Answers
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Where can I learn how to write C code to speed up slow R functions? [closed]
...ds C++ and Rcpp to be much more like writing R than writing C++. YMMV and all that.
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npm install vs. update - what's the difference?
What is the practical difference between npm install and npm update ? When should I use which?
5 Answers
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What is the difference between C# and .NET?
.... The C# specification says only a very little about the environment (basically, that it should contain some types such as int, but that's more or less all).
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JPA : How to convert a native query result set to POJO class collection
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JPA provides an SqlResultSetMapping that allows you to map whatever returns from your native query into an Entity or a custom class.
EDIT JPA 1.0 does not allow mapping to non-entity classes. Only in JPA 2.1 a ConstructorResult has been added to map return values a...
How do I use IValidatableObject?
... Prop1 = 1,
Prop2 = 2
};
bool validateAllProperties = false;
var results = new List<ValidationResult>();
bool isValid = Validator.TryValidateObject(
toValidate,
new ValidationContext(toValidate, null, null),
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Why don't Java Generics support primitive types?
...nerics in Java are an entirely compile-time construct - the compiler turns all generic uses into casts to the right type. This is to maintain backwards compatibility with previous JVM runtimes.
This:
List<ClassA> list = new ArrayList<ClassA>();
list.add(new ClassA());
ClassA a = list.g...
Using a strategy pattern and a command pattern
...s encapsulate an algorithm and decouple implementation details from their calling classes. The only difference I can discern is that the Strategy pattern takes in parameters for execution, while the Command pattern doesn't.
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