大约有 40,000 项符合查询结果（耗时：0.0451秒） [XML]
Select distinct values from a table field
...ant any ordering to be applied to a query, not even the default ordering, call order_by() with no parameters.
and distinct() in the note where it discusses issues with using distinct() with ordering.
To query your DB, you just have to call:
models.Shop.objects.order_by().values('city').distinct(...
How do you trigger a block after a delay, like -performSelector:withObject:afterDelay:?
Is there a way to call a block with a primitive parameter after a delay, like using performSelector:withObject:afterDelay: but with an argument like int / double / float ?
...
Is it possible to push a git stash to a remote repository?
...ffect either!
It would only be confusing anyway since that wouldn't fetch all stashes, only the latest one; the list of stashes is the reflog of the ref refs/stashes.
share
|
improve this answer
...
Find the PID of a process that uses a port on Windows
...t on Windows (e.g. port: "9999")
netstat -aon | find "9999"
-a Displays all connections and listening ports.
-o Displays the owning process ID associated with each connection.
-n Displays addresses and port numbers in numerical form.
Output:
TCP 0.0.0.0:9999 0.0.0.0:0 LISTENING...
Ruby on Rails: Delete multiple hash keys
...re unaware of the Hash#except method ActiveSupport adds to Hash.
It would allow your code to be simplified to:
redirect_to my_path(params.except(:controller, :action, :other_key))
Also, you wouldn't have to monkey patch, since the Rails team did it for you!
...
Ruby send vs __send__
I understand the concept of some_instance.send but I'm trying to figure out why you can call this both ways. The Ruby Koans imply that there is some reason beyond providing lots of different ways to do the same thing. Here are the two examples of usage:
...
How can I count the occurrences of a list item?
...1, 4, 1].count(1)
3
Don't use this if you want to count multiple items. Calling count in a loop requires a separate pass over the list for every count call, which can be catastrophic for performance. If you want to count all items, or even just multiple items, use Counter, as explained in the othe...
Is it better to use Enumerable.Empty() as opposed to new List() to initialize an IEnumerable
...uld be noticeable impact.
Enumerable.Empty does not create an object per call thus putting less load on GC.
If the code is in low-throughput location, then it boils down to aesthetic considerations though.
share
|...
Code Golf - π day
...
Yeah, the ( operator alone allowed to shed 6 strokes!
– Dan Andreatta
Mar 18 '10 at 10:25
add a comment
|
...
Can I mix MySQL APIs in PHP?
...where. (Not sure whether plain old resources do that, but objects can actually take advantage of RAII to a not-insignificant degree.)
– cHao
Jul 5 '13 at 23:54
...