大约有 6,700 项符合查询结果（耗时：0.0301秒） [XML]
Only read selected columns
...ery(conn, "select * from mtcars"), 3)
mpg cyl disp hp drat wt qsec vs am gear carb
1 21 6 160 110 3.9 2.62 16.46 0 1 4 4
2 21 6 160 110 3.9 2.875 17.02 0 1 4 4
3 22.8 4 108 93 3.85 2.32 18.61 1 1 4 1
> head(dbGetQuery(conn, "select mpg, gear from...
what is faster: in_array or isset? [closed]
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Which is faster: isset() vs in_array()
isset() is faster.
While it should be obvious, isset() only tests a single value. Whereas in_array() will iterate over the entire array, testing the value of each element.
Rough benchmarking is quite easy us...
How to view the assembly behind the code using Visual C++?
...hen compiling a static library with whole-program optimization enabled (in VS2010 at least). Which makes sense - the compiler hasn't generated the final code yet.
– dhaffey
Mar 26 '13 at 18:45
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How can I check if a Perl array contains a particular value?
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@eakssjo's benchmark is broken - measures creating hashes in loop vs creating regexes in loop. Fixed version (plus I've added List::Util::first and List::MoreUtils::any):
use List::Util qw(first);
use List::MoreUtils qw(any);
use Benchmark;
my @list = ( 1..10_000 );
my $hit = 5_000;
my $h...
MySQL Error 1215: Cannot add foreign key constraint
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Collation was my issue, latin1 vs utf8 (check the table AND the column).
– ben_979
Apr 28 '16 at 1:15
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Replacement for deprecated sizeWithFont: in iOS 7?
....0f] with label.font - helps code maintenance by referencing existing data vs. you typing it multiple times or referencing constants all over the place, etc
– toblerpwn
Oct 30 '13 at 21:38
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How to output something in PowerShell
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I think the following is a good exhibit of Echo vs. Write-Host. Notice how test() actually returns an array of ints, not a single int as one could easily be led to believe.
function test {
Write-Host 123
echo 456 # AKA 'Write-Output'
return 789
}
$x = test
W...
How do you pass custom environment variable on Amazon Elastic Beanstalk (AWS EBS)?
...nvironment variables is not the same for getting a property.
System.getenv vs System.getProperty
I ssh'd into the box and verified that the environment variable was never set. However, in the tomcat logs I can see the -D property is set.
I've changed my code to check for both locations now as a wo...
How can I retrieve Id of inserted entity using Entity framework? [closed]
...://www.ladislavmrnka.com/2011/03/the-bug-in-storegeneratedpattern-fixed-in-vs-2010-sp1/
You have to set the property of StoreGeneratedPattern to identity and then try your own code.
Or else you can also use this.
using (var context = new MyContext())
{
context.MyEntities.AddObject(myNewObject);...
Convert objective-c typedef to its string equivalent
...n, so it's only created once and stays in memory otherwise. Classic memory vs. CPU conundrum.
– Joel Fischer
Apr 11 '14 at 14:24
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