大约有 47,000 项符合查询结果（耗时：0.0755秒） [XML]
How to count occurrences of a column value efficiently in SQL?
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edited Oct 1 '09 at 16:38
answered Oct 1 '09 at 13:30
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Speed up the loop operation in R
... accumulates something. (simple operation). The data.frame has roughly 850K rows. My PC is still working (about 10h now) and I have no idea about the runtime.
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Revert the `--no-site-packages` option with virtualenv
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edited Oct 23 '19 at 0:14
Zain Rizvi
20.7k1717 gold badges7878 silver badges119119 bronze badges
an...
Mongoose's find method with $or condition does not work properly
...pes.ObjectId;
var objId = new ObjectId( (param.length < 12) ? "123456789012" : param );
// You should make string 'param' as ObjectId type. To avoid exception,
// the 'param' must consist of more than 12 characters.
User.find( { $or:[ {'_id':objId}, {'name':param}, {'nickname':param} ]},
fun...
PHP - Modify current object in foreach loop
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207
There are 2 ways of doing this
foreach($questions as $key => $question){
$questions[$ke...
Convert data.frame column format from character to factor
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201
Hi welcome to the world of R.
mtcars #look at this built in data set
str(mtcars) #allows you ...
Unable to create a constant value of type Only primitive types or enumeration types are supported in
...aumaSlauma
164k5555 gold badges377377 silver badges404404 bronze badges
10
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Regular expression to allow spaces between words
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tl;dr
Just add a space in your character class.
^[a-zA-Z0-9_ ]*$
Now, if you want to be strict...
The above isn't exactly correct. Due to the fact that * means zero or more, it would match all of the following cases that one would not usually mean to match:
An empty str...
How to Reverse Fragment Animations on BackStack?
...wered Jun 4 '12 at 18:56
user742030user742030
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Set default CRAN mirror permanent in R
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edited May 20 '19 at 19:22
miguelmorin
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