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Unique constraint on multiple columns
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By using the constraint definition on table creation, you can specify one or multiple constraints that span multiple columns. The syntax, simplified from technet's documentation, is in the form of:
CONSTRAINT constraint_name UNIQUE [ CLUSTERED | NONCLUSTERED ]
(
column [ ASC | DESC ] ...
How does BLAS get such extreme performance?
...evel1 functions. However, you can boost the performance of this functions if you can provide a dedicated implementation that makes use of some multiprocessor architecture with shared memory.
Level 3 functions are operations like the matrix-matrix product. Again you could implement them in terms o...
jQuery $.ajax(), $.post sending “OPTIONS” as REQUEST_METHOD in Firefox
...n policy. It only allows you to do XMLHTTPRequests to your own domain. See if you can use a JSONP callback instead:
$.getJSON( 'http://<url>/api.php?callback=?', function ( data ) { alert ( data ); } );
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Click through div to underlying elements
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Also nice to know...
You can disable pointer-events in a parent element (probably transparent div) but have it still enabled for its child elements.
This is helpful if you work with multiple overlapping div layers, where you want to be abl...
UIView Infinite 360 degree rotation animation?
...de for iOS 3.0 and below but for newer programmers and new projects, Apple now warns users away from these methods in the Docs & @Nate code uses the block based animations that Apple now prefers
– PaulWoodIII
May 15 '13 at 4:46
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How to quickly check if folder is empty (.NET)?
I have to check, if directory on disk is empty. It means, that it does not contain any folders/files. I know, that there is a simple method. We get array of FileSystemInfo's and check if count of elements equals to zero. Something like that:
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Why does sudo change the PATH?
...annoying function" prevents you from getting trojaned. I say forcing a specific $PATH is a feature, not a bug---it makes you write out the full path to a program that's outside the $PATH.
– Chris Jester-Young
May 18 '09 at 16:10
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Is gcc std::unordered_map implementation slow? If so - why?
...m to be pointing to "fixes" to max_load_factor handling, which led to the difference in performance.
– jxh
Jul 24 '12 at 18:21
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OS X Bash, 'watch' command
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I believe watch only shows the first screenful of output. If you want to do something similar, change your_command to your_command 2>&1|head -10
– Mark Eirich
Nov 10 '13 at 15:36
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Why doesn't GCC optimize a*a*a*a*a*a to (a*a*a)*(a*a*a)?
I am doing some numerical optimization on a scientific application. One thing I noticed is that GCC will optimize the call pow(a,2) by compiling it into a*a , but the call pow(a,6) is not optimized and will actually call the library function pow , which greatly slows down the performance. (In ...