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mongodb group values by multiple fields
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This turns out to be very difficult to do, but it can be done though the complexity just increases with the number of items you need to match. To keep it simple we can keep this at 2 matches at most:
db.books.aggregate([
{ "$group": {
"_id": {
"addr": "$addr",
"...
ASP MVC href to a controller/view
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There are a couple of ways that you can accomplish this. You can do the following:
<li>
@Html.ActionLink("Clients", "Index", "User", new { @class = "elements" }, null)
</li>
or this:
<li>
<a href="@Url.Action("Index", "Users")" clas...
How to specify jackson to only use fields - preferably globally
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151
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RabbitMQ and relationship between channel and connection
...nto
a Channel are serialized, with only one thread being able to run a
command on the Channel at a time. Even so, applications should prefer
using a Channel per thread instead of sharing the same Channel across
multiple threads.
There is no direct relation between Channel and Queue. A Chan...
How to change line-ending settings
...tocrlf"
If you want to know what file this is saved in, you can run the command:
git config --global --edit
and the git global config file should open in a text editor, and you can see where that file was loaded from.
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How do I install an R package from source?
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98
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Iterate all files in a directory using a 'for' loop
...the current directory:
for /r %i in (*) do echo %i
Also if you run that command in a batch file you need to double the % signs.
for /r %%i in (*) do echo %%i
(thanks @agnul)
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show all tags in git log
Why does git log --decorate not display more than one tag per commit?
3 Answers
3
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Why doesn't c++ have &&= or ||= for booleans?
...forming C++ code.
1 Admittedly this is a rather big caveat as Angew’s comment illustrates:
bool b = true;
b &= 2; // yields `false`.
The reason is that b & 2 performs integer promotion such that the expression is then equivalent to static_cast<int>(b) & 2, which results in ...