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count(*) vs count(column-name) - which is more correct? [duplicate]
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COUNT(*) counts all rows
COUNT(column) counts non-NULLs only
COUNT(1) is the same as COUNT(*) because 1 is a non-null expressions
Your use of COUNT(*) or COUNT(column) should be based on the desired output only.
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PHP $_SERVER['HTTP_HOST'] vs. $_SERVER['SERVER_NAME'], am I understanding the man pages correctly?
...you either go with that or you check the host name against a white list:
$allowed_hosts = array('foo.example.com', 'bar.example.com');
if (!isset($_SERVER['HTTP_HOST']) || !in_array($_SERVER['HTTP_HOST'], $allowed_hosts)) {
header($_SERVER['SERVER_PROTOCOL'].' 400 Bad Request');
exit;
}
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Equals(=) vs. LIKE
...tify an example where these operators produce obviously different results. Allow me to quote from the MySQL manual:
Per the SQL standard, LIKE performs matching on a per-character basis, thus it can produce results different from the = comparison operator:
mysql> SELECT 'ä' LIKE 'ae' COLLA...
How to keep the console window open in Visual C++?
...ause") or any other garbage. Changing this works.
– Callat
Apr 22 '16 at 16:08
Ctrl+F5 means 'Start Without Debugging'...
map vs. hash_map in C++
...tied to that key.
map is implemented as a balanced binary search tree (usually a red/black tree).
An unordered_map should give slightly better performance for accessing known elements of the collection, but a map will have additional useful characteristics (e.g. it is stored in sorted order, which...
throw Error('msg') vs throw new Error('msg')
...this is explicitly stated in the specification:
... Thus the function call Error(…) is equivalent to the object creation expression new Error(…) with the same arguments.
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Benchmarking (python vs. c++ using BLAS) and (numpy)
...e python for my program, what could I do to increase the performance when calling BLAS or LAPACK routines?
Make sure that numpy uses optimized version of BLAS/LAPACK libraries on your system.
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十年磨一“饼” 一个70后连续创业者的心路历程 - 资讯 - 清泛网 - 专注C/C+...
...异国不能加入我们的创业团队……
初期，为了寻找产品开发的灵感，我的足迹踏遍台北-日本-广州-北京-上海-香港，期间还请教了赛百味亚洲总部的ALAN老师关于很多标准化和供应链的问题(他在新加坡亚洲总部负责产品开发及供...
Named routes _path vs _url
...01346#221052
and, here:
http://viget.com/extend/rails-named-routes-path-vs-url
You can also take a look at the relevant section of the HTTP specification here:
http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.30
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HTML input - name vs. id [duplicate]
... is the difference between the use of the name and id attributes especially that I found that they are sometimes named the same?
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