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What's the $unwind operator in MongoDB?
...
Or another way to think of it is UNION ALL
– Jeb50
Apr 9 '17 at 23:44
add a comment
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Select first row in each GROUP BY group?
... FROM purchases
ORDER BY customer_id, total DESC
LIMIT 1
)
UNION ALL
SELECT u.*
FROM cte c
, LATERAL (
SELECT id, customer_id, total
FROM purchases
WHERE customer_id > c.customer_id -- lateral reference
ORDER BY customer_id, total DESC
...
Big-O for Eight Year Olds? [duplicate]
.... As a rough category, I would include algorithms such as hash lookups and Union-Find here, even though neither of those are actually O(1).
O(log(n)) "logarithmic" - it gets slower as you get larger inputs, but once your input gets fairly large, it won't change enough to worry about. If your runtime...
How can I add reflection to a C++ application?
...ble with C++.
Inspection by checking whether a class-type (class, struct, union) has a method or nested type, is derived from another particular type.
This kind of thing is possible with C++ using template-tricks. Use boost::type_traits for many things (like checking whether a type is integral). Fo...
How is “=default” different from “{}” for default constructor and destructor?
...le default
constructor);
— if T is a (possibly cv-qualified) non-union class type
without a user-provided constructor, then the object is
zero-initialized and, if T’s implicitly-declared default constructor
is non-trivial, that constructor is called.
— if T is an array type,...
typedef struct vs struct definitions [duplicate]
...a typedef can make C code more C++-like. In C++, structs (and classes, and unions, and enums) are referred to using a name that's a single identifier. Referring to a type as struct foo is more C-like.
– Keith Thompson
Feb 9 at 22:19
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Questions every good .NET developer should be able to answer? [closed]
...nstances on this site where people are trying to roll their own version of Union Distinct and Concat for collections because they don't understand LINQ.
– Evan Plaice
Jun 19 '10 at 1:04
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Rails has_and_belongs_to_many migration
...e. From the docs
By default, the name of the join table comes from the union of the
first two arguments provided to create_join_table, in alphabetical
order. To customize the name of the table, provide a :table_name
option:
...
C++ performance challenge: integer to std::string conversion
...; 32) + (k));
}
template <typename T>
std::string itostr(T o) {
union {
char str[16];
unsigned short u2[8];
unsigned u4[4];
unsigned long long u8[2];
};
unsigned v = o < 0 ? ~o + 1 : o;
u8[0] = (ull(v) * 3518437209u) >> 45;
u8[0] ...
What are rvalues, lvalues, xvalues, glvalues, and prvalues?
...of rvalue, i.e. they're the rvalues that aren't xvalues.
Glvalues are the union of xvalues and lvalues in one group, because they do share a lot of properties in common.
So really, it all comes down to xvalues and the need to restrict movement to exactly and only certain places. Those places are ...