大约有 40,000 项符合查询结果（耗时：0.0499秒） [XML]
Difference between a theta join, equijoin and natural join
... yourself).
** I don't quite know what the result of SELECT * FROM table_expression; is. I know it is not a relation because, among other reasons, it can have columns with duplicate names or a column with no name. I know it is not a set because, among other reasons, the column order is significan...
Regex lookahead, lookbehind and atomic groups
...pression.info for more details.
Positive lookahead:
Syntax:
(?=REGEX_1)REGEX_2
Match only if REGEX_1 matches; after matching REGEX_1, the match is discarded and searching for REGEX_2 starts at the same position.
example:
(?=[a-z0-9]{4}$)[a-z]{1,2}[0-9]{2,3}
REGEX_1 is [a-z0-9]{4}$ which...
Dealing with commas in a CSV file
....Read ) )
{
}
public CsvReader( Stream stream )
{
__reader = new StreamReader( stream );
}
public System.Collections.IEnumerable RowEnumerator
{
get {
if ( null == __reader )
throw new System.ApplicationException( "I can't sta...
How do you overcome the HTML form nesting limitation?
.../post/dispatch/clone" />
</div>
http://www.whatwg.org/specs/web-apps/current-work/#attributes-for-form-submission
The advantage of these new features is that they do all this declaratively without JavaScript. The disadvantage is that they are not supported on older browsers, so you'd hav...
Meaning of @classmethod and @staticmethod for beginner? [duplicate]
...thod can have no parameters at all.
Example
class Date(object):
def __init__(self, day=0, month=0, year=0):
self.day = day
self.month = month
self.year = year
@classmethod
def from_string(cls, date_as_string):
day, month, year = map(int, date_as_string...
Convert json data to a html table [closed]
...in vanilla-js, using DOM methods to prevent html injection.
Demo
var _table_ = document.createElement('table'),
_tr_ = document.createElement('tr'),
_th_ = document.createElement('th'),
_td_ = document.createElement('td');
// Builds the HTML Table out of myList json data from Ivy r...
Android Activity as a dialog
...gt;
Use this property inside your activity tag to avoid that your Dialog appears in the recently used apps list
android:excludeFromRecents="true"
If you want to stop your dialog / activity from being destroyed when the user clicks outside of the dialog:
After setContentView() in your Activity...
Does MongoDB's $in clause guarantee order
...ly have two options.
So let's say that you were matching on the values of _id in your documents with an array that is going to be passed in to the $in as [ 4, 2, 8 ].
Approach using Aggregate
var list = [ 4, 2, 8 ];
db.collection.aggregate([
// Match the selected documents by "_id"
...
Callback functions in C++
...ard algorithms library <algorithm> use callbacks. For example the for_each algorithm applies an unary callback to every item in a range of iterators:
template<class InputIt, class UnaryFunction>
UnaryFunction for_each(InputIt first, InputIt last, UnaryFunction f)
{
for (; first != las...
Python dictionary: Get list of values for list of keys
...n list-comp:
Build list and throw exception if key not found: map(mydict.__getitem__, mykeys)
Build list with None if key not found: map(mydict.get, mykeys)
Alternatively, using operator.itemgetter can return a tuple:
from operator import itemgetter
myvalues = itemgetter(*mykeys)(mydict)
# use ...