大约有 40,000 项符合查询结果（耗时：0.0444秒） [XML]
Difference between Select Unique and Select Distinct
...
SELECT UNIQUE is old syntax supported by Oracle's flavor of SQL. It is synonymous with SELECT DISTINCT.
Use SELECT DISTINCT because this is standard SQL, and SELECT UNIQUE is non-standard, and in database brands other than Oracle, SELECT UNIQUE may not be recog...
What is lexical scope?
... access its outer levels.
There is another way, called dynamic scope used by the first implementation of Lisp, again in a C-like syntax:
void fun()
{
printf("%d", x);
}
void dummy1()
{
int x = 5;
fun();
}
void dummy2()
{
int x = 10;
fun();
}
Here fun can either access x i...
Callback functions in C++
...d why to use them(!)
A callback is a callable (see further down) accepted by a class or function, used to customize the current logic depending on that callback.
One reason to use callbacks is to write generic code which is independant from the logic in the called function and can be reused with d...
Change auto increment starting number?
...ment value, and the change will be applied instantly.
You can verify this by issuing a SHOW CREATE TABLE t statement. You should see:
> SHOW CREATE TABLE t \G
*************************** 1. row ***************************
Table: t
Create Table: CREATE TABLE `t` (
...
) ENGINE=InnoDB AUTO...
Relatively position an element without it taking up space in document flow
...ning. On the other hand, you can, however, make a pseudo-relative element, by creating a zero-width, zero-height, relatively positioned element, essentially solely for the purpose of creating a reference point for position, and an absolutely positioned element within that:
<div style="position: ...
Using Pylint with Django
...
Do not disable or weaken Pylint functionality by adding ignores or generated-members.
Use an actively developed Pylint plugin that understands Django.
This Pylint plugin for Django works quite well:
pip install pylint-django
and when running pylint add the following f...
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
...nnection refused
I'm quoting from this answer which also contains a step-by-step MySQL+JDBC tutorial:
If you get a SQLException: Connection refused or Connection timed out or a MySQL specific CommunicationsException:
Communications link failure, then it means that the DB isn't reachable at ...
What is the advantage of using Restangular over ngResource?
...ruct the $resource object for this manually. Restangular helps you in this by "remembering" the URLs.
So if you do in some place
Restangular.one("users", 123).get().then(function(user) {
$scope.user = user;
});
// Some other code
//Automatically does the request to /users/123/cars as it rememb...
Why is using a wild card with a Java import statement bad?
...identified here (e.g. java.sql.Date vs java.util.Date) are easily remedied by other means, not really addressed by specific imports and certainly do not justify insanely pedantic imports on all classes. There is nothing more disconcerting than opening a source file and having to page through 100 im...
Why does C++ not have reflection?
...as to be
there, so that reflection can find
it. Part of this is alleviated by C#
compiling to bytecode, which means
that the JIT compiler can remove
class definitions and inline
functions if it likes, even if the
initial C# compiler can't. In C++,
you only have one compiler, and it
has to output eff...