大约有 30,000 项符合查询结果（耗时：0.0490秒） [XML]
In Postgresql, force unique on combination of two columns
...
CREATE TABLE someTable (
id serial primary key,
col1 int NOT NULL,
col2 int NOT NULL,
unique (col1, col2)
)
autoincrement is not postgresql. You want a serial.
If col1 and col2 make a unique and can't be null then they make a good prim...
How to define optional methods in Swift protocol?
...ust always check if an optional method is implemented by either optionally calling or checking if the conforming type implements it. This might introduce a lot of boilerplate if you're calling optional methods often.
share
...
My Understanding of HTTP Polling, Long Polling, HTTP Streaming and WebSockets
...
Also note that there is a W3C proposal for standardizing HTTP streaming called Server-Sent Events. It is currently fairly early in it's evolution and is designed to provide a standard Javascript API with comparable simplicity to WebSockets.
...
Virtual Serial Port for Linux
...verything it does via /dev/ptyp5.
If you really need it to talk to a file called /dev/ttys2, then simply move your old /dev/ttys2 out of the way and make a symlink from ptyp5 to ttys2.
Of course you can use some number other than ptyp5. Perhaps pick one with a high number to avoid duplicates, sin...
JavaScript: how to change form action attribute value based on selection?
...
Simple and easy in javascipt
<script>
document.getElementById("selectsearch").addEventListener("change", function(){
var get_form = document.getElementById("search-form") // get form
get_form.action = '/search/' + this.value; // assign value
});
</script>
...
Random record from MongoDB
...t would have the fatal flaw of not matching anything if the $sample stage didn't select any matching documents.
– JohnnyHK
Apr 19 at 0:21
...
When to use “new” and when not to, in C++? [duplicate]
...of 'p' will be where its containing object, Foo, is allocated. I prefer to call this 'in-place' allocation.
class Foo
{
Point p;
}; // p will be automatically destroyed when foo is.
Allocating (and freeing) objects with the use of new is far more expensive than if they are allocated in-place s...
To underscore or to not to underscore, that is the question
... other framework languages? For example since C# is case-sensitive you can call a field "foo" and the public property "Foo" and it works fine.
...
Access denied for user 'root'@'localhost' while attempting to grant privileges. How do I grant privi
...
Notice how the output of
SHOW GRANTS FOR 'root'@'localhost';
did not say 'ALL PRIVILEGES' but had to spell out what root@localhost has.
GRANT ALL PRIVILEGES will fail, because a user can not grant what he/she does not have,
and the server seem to think something is not here ...
Now, w...
Problem getting the AssemblyVersion into a web page using Razor /MVC3
...
You could try to use the GetCallingAssembly(). I'm not sure if that is high enough up the call stack or not, but since Razor actually creates an assembly for each view, it stands to reason that your app would be the calling assembly for the view assembl...