大约有 12,000 项符合查询结果（耗时：0.0261秒） [XML]
MySQL select 10 random rows from 600K rows fast
...s 0.35s on my machine.
This is fast because the sort phase only uses the indexed ID column. You can see this behaviour in the explain:
SELECT * FROM tbl ORDER BY RAND() LIMIT 10:
SELECT * FROM tbl AS t1 JOIN (SELECT id FROM tbl ORDER BY RAND() LIMIT 10) as t2 ON t1.id=t2.id
Weighted Version: ...
Why can't decimal numbers be represented exactly in binary?
There have been several questions posted to SO about floating-point representation. For example, the decimal number 0.1 doesn't have an exact binary representation, so it's dangerous to use the == operator to compare it to another floating-point number. I understand the principles behind floating-po...
How to check if a string array contains one string in JavaScript? [duplicate]
...
There is an indexOf method that all arrays have (except Internet Explorer 8 and below) that will return the index of an element in the array, or -1 if it's not in the array:
if (yourArray.indexOf("someString") > -1) {
//In the ar...
Create a CSS rule / class with jQuery at runtime
...t/css")
.html("\
#my-window {\
position: fixed;\
z-index: 102;\
display:none;\
top:50%;\
left:50%;\
}")
.appendTo("head");
Noticed the back slashes? They are used to join strings that are on new lines. Leaving them out generates an error.
...
Disable validation of HTML5 form elements
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@user1569050 For example in frameworks like CakePHP, it will use the novalidate="novalidate" method when you set the novalidate => true in the $options array of the FormHelper::create(). Thanks bassim for the extra info :)
– Jelmer
...
How do I change the cursor between Normal and Insert modes in Vim?
...ash with ConEmu on Windows; and more (see comments):
let &t_SI = "\e[6 q"
let &t_EI = "\e[2 q"
" Optionally reset the cursor on start:
augroup myCmds
au!
autocmd VimEnter * silent !echo -ne "\e[2 q"
augroup END
Other options (replace the number after \e[):
Ps = 0 -> blinking block.
Ps ...
How to test if string exists in file with Bash?
...
grep -Fxq "$FILENAME" my_list.txt
The exit status is 0 (true) if the name was found, 1 (false) if not, so:
if grep -Fxq "$FILENAME" my_list.txt
then
# code if found
else
# code if not found
fi
Explanation
Here are the relev...
How does Access-Control-Allow-Origin header work?
...t using this header for POST and GET requests. I had accidently opened the index.html file directly from disk, so the URL the client was accessing on node.js was thought to be cross-domain, while it was simply running on localhost. Accessing via the URL (as one would usually do) "solved" my issue......
How do I show a marker in Maps launched by geo URI Intent?
...t = new Intent(Intent.ACTION_VIEW, Uri.parse("geo:<lat>,<long>?q=<lat>,<long>(Label+Name)"));
startActivity(intent);
You can omit (Label+Name) if you don't want a label, and it will choose one randomly based on the nearest street or other thing it thinks relevant.
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How do I exit the Vim editor?
...e of the following commands. To execute a command, press the Enter key.
:q to quit (short for :quit)
:q! to quit without saving (short for :quit!)
:wq to write and quit
:wq! to write and quit even if file has only read permission (if file does not have write permission: force write)
:x to write ...