大约有 44,611 项符合查询结果（耗时：0.0515秒） [XML]
SQL select only rows with max value on a column [duplicate]
...
At first glance...
All you need is a GROUP BY clause with the MAX aggregate function:
SELECT id, MAX(rev)
FROM YourTable
GROUP BY id
It's never that simple, is it?
I just noticed you need the content column as well.
This is a very common question in SQL: find the whole data...
NSUserDefaults - How to tell if a key exists
...small iPhone app, and I am using NSUserDefaults as my data persistence. It only has to keep track of a few things, such as some names and some numbers so I figure I might as well keep it simple.
...
Double exclamation points? [duplicate]
...lse.
!!"foo" // Evaluates to true.
If foo.bar is passed through, then it may not be 0 but some other falsy value. See the following truth table:
Truth Table for javascript
'' == '0' // false
0 == '' // true
0 == '0' // true
false ...
Setting Objects to Null/Nothing after use in .NET
...et all the objects to null ( Nothing in VB.NET) once you have finished with them?
15 Answers
...
Can you set a border opacity in CSS?
...traight forward CSS way to make the border of an element semi-transparent with something like this?
9 Answers
...
How to handle configuration in Go [closed]
...
The JSON format worked for me quite well. The
standard library offers methods to write the data structure indented, so it is quite
readable.
See also this golang-nuts thread.
The benefits of JSON are that it is fairly simple to parse and human readable/ed...
Is there a performance difference between i++ and ++i in C?
....
We can demonstrate this by looking at the code for this function,
both with ++i and i++.
$ cat i++.c
extern void g(int i);
void f()
{
int i;
for (i = 0; i < 100; i++)
g(i);
}
The files are the same, except for ++i and i++:
$ diff i++.c ++i.c
6c6
< for (i = 0; i <...
insert vs emplace vs operator[] in c++ map
... I will start explaining those.
The operator[] is a find-or-add operator. It will try to find an element with the given key inside the map, and if it exists it will return a reference to the stored value. If it does not, it will create a new element inserted in place with default initialization and...
Mapping a function on the values of a map in Clojure
I want to transform one map of values to another map with the same keys but with a function applied to the values. I would think there was a function for doing this in the clojure api, but I have been unable to find it.
...
Programmatically open Maps app in iOS 6
...
Here's the official Apple way:
// Check for iOS 6
Class mapItemClass = [MKMapItem class];
if (mapItemClass && [mapItemClass respondsToSelector:@selector(openMapsWithItems:launchOptions:)])
{
// Create an MKMapItem to pass to the Maps app
CLLocationCoordinate2D coordi...