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SQL WHERE.. IN clause multiple columns
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While this would work, it converts the uncorrelated query in the question into a correlated query. Unless the query optimizer is clever, this might give you O(n^2) performance :-(. But maybe I'm underestimating the optimizer...
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Using Rails serialize to save hash to database
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add_column :users, :multi_wrong, :text
end
Then Rails will properly convert it into YAML for you (and perform proper serialization). Strings fields are limited in size and will only hold especially-small values.
share...
How do I make class methods / properties in Swift?
... static var all = [Foo]() // static type property
class var comp: Int { // computed type property
return 42
}
class func alert() { // type method
print("There are \(all.count) foos")
}
}
Foo.alert() // There are 0 foos
let f = Foo()
Foo.all.a...
How do I check if a given string is a legal/valid file name under Windows?
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2nd piece of code doesn't compile. "Cannot convert from char[] to string
– Paul Hunt
Apr 25 '14 at 12:03
1
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Should I use an exception specifier in C++?
... extensibility.
virtual void open() throw( FileNotFound );
might evolve into
virtual void open() throw( FileNotFound, SocketNotReady, InterprocessObjectNotImplemented, HardwareUnresponsive );
You could really write that as
throw( ... )
The first is not extensible, the second is overambitiou...
How to initialize HashSet values by construction?
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Again, this is not time efficient since you are constructing an array, converting to a list and using that list to create a set.
When initializing static final sets I usually write it like this:
public static final String[] SET_VALUES = new String[] { "a", "b" };
public static final Set<Str...
HTML select form with option to enter custom value
...ext, to a GET of the same page as a query string. Does anyone know how to convert the action to a POST, so I can grab the value in a php file and do something with it there?
– Han
Sep 29 '19 at 8:17
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In C#, how can I create a TextReader object from a string (without writing to disk)
...es a TextReader object, and all I have is a string. What's the best way to convert a string into a TextReader object on the fly?
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What is the purpose of static keyword in array parameter of function like “char s[static 10]”?
...ameter as ‘‘array of type’’ shall be adjusted to ‘‘qualified pointer to type’’, where the type qualifiers (if any) are those specified within the [ and ] of the array type derivation. If the keyword static also appears within the [ and ] of the array type derivation, then for each ca...
What is the difference between pluck and collect in Rails?
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Yes. According to Rails guides, pluck directly converts a database result into an array, without constructing ActiveRecord objects. This means better performance for a large or often-running query.
In addition to @apneadiving's answer, pluck can take both single and mult...