大约有 40,000 项符合查询结果（耗时：0.0377秒） [XML]
MySQL和MongoDB设计实例进行对比 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...查询：
db.getCollection("mobiles").find({
"params": {
$all: [
{$elemMatch: {"name": "待机时间", "value": {$gt: 100}}},
{$elemMatch: {"name": "外观设计", "value": "直板"}}
]
}
});
注：查询中用到的$all，$elemMatch等高...
Temporarily disable auto_now / auto_now_add
...s:
# my model
class FooBar(models.Model):
title = models.CharField(max_length=255)
updated_at = models.DateTimeField(auto_now=True, auto_now_add=True)
# my tests
foo = FooBar.objects.get(pk=1)
# force a timestamp
lastweek = datetime.datetime.now() - datetime.timedelta(days=7)
FooBar.obj...
Retrieve database or any other file from the Internal Storage using run-as
...nly copy DBs from the Debug variant of your app. If this happens, just install the debug variant and try the command again. Hope this helps someone.
– Aonghus Shortt
Apr 14 '17 at 18:02
...
count(*) vs count(column-name) - which is more correct? [duplicate]
...
COUNT(*) counts all rows
COUNT(column) counts non-NULLs only
COUNT(1) is the same as COUNT(*) because 1 is a non-null expressions
Your use of COUNT(*) or COUNT(column) should be based on the desired output only.
...
Why does Javascript's regex.exec() not always return the same value? [duplicate]
... matches by performing the assignment as the loop condition.
var re = /foo_(\d+)/g,
str = "text foo_123 more text foo_456 foo_789 end text",
match,
results = [];
while (match = re.exec(str))
results.push(+match[1]);
DEMO: http://jsfiddle.net/pPW8Y/
If you don't like the placem...
How do I show a Save As dialog in WPF?
...alog dialog = new SaveFileDialog()
{
Filter = "Text Files(*.txt)|*.txt|All(*.*)|*"
};
if (dialog.ShowDialog() == true)
{
File.WriteAllText(dialog.FileName, fileText);
}
share
|
improve th...
Getting key with maximum value in dictionary?
...
@oba2311 max_value = max(stats.values()); {key for key, value in stats.items() if value == max_value}
– A. Coady
Apr 4 '17 at 0:37
...
lenses, fclabels, data-accessor - which library for structure access and mutation is better
...f these libraries also provide a bunch of extra combinators on top, and usually some form of template haskell machinery to automatically generate lenses for the fields of simple record types.
With that in mind, we can turn to the different implementations:
Implementations
fclabels
fclabels is pe...
Rename multiple files based on pattern in Unix
...
Not present on all *nix systems. Not on Max OS X for one, and no package in fink to get it. Haven't looked at MacPorts.
– dmckee --- ex-moderator kitten
Jul 6 '09 at 16:07
...
What is the difference between lock and Mutex?
...hine.
bool firstInstance;
Mutex mutex = new Mutex(false, @"Local\DASHBOARD_MAIN_APPLICATION", out firstInstance);
if (!firstInstance)
{
//another copy of this application running
}
else
{
//run main application loop here.
}
// Refer to the mutex down here so garbage collection doesn't chu...