PHP: Get the Latest File Addition in a Directory – Stack Overflow
$path = "/path/to/my/dir";
$latest_ctime = 0;
$latest_filename = '';
$d = dir($path);
while (false !== ($entry = $d->read())) {
$filepath = "{$path}/{$entry}";
// could do also other checks than just checking whether the entry is a file
if (is_file($filepath) && filectime($filepath) > $latest_ctime) {
$latest_ctime = filectime($filepath);
$latest_filename = $entry;
}
}How to change apache2 default charset in Ubuntu | Ubuntu Geek
If you want to change the apache2 default charset in Ubuntu try this procedure
You need to edit this file
/etc/apache2/conf.d/charset
sudo gedit /etc/apache2/conf.d/charset
next you should change the line
#AddDefaultCharset ISO-8859-1
to
AddDefaultCharset {YOUR_DEFAULT_CHARSET | Example: UTF-8}
save and exit the file
Now you need to restart the apache server using the following command
sudo /etc/init.d/apache2 restart
Task: For each article, find the dealer or dealers with the most expensive price.
This problem can be solved with a subquery like this one:
SELECT article, dealer, price
FROM shop s1
WHERE price=(SELECT MAX(s2.price)
FROM shop s2
WHERE s1.article = s2.article);
+---------+--------+-------+
| article | dealer | price |
+---------+--------+-------+
| 0001 | B | 3.99 |
| 0002 | A | 10.99 |
| 0003 | C | 1.69 |
| 0004 | D | 19.95 |
+---------+--------+-------+
The preceding example uses a correlated subquery, which can be inefficient (see Section 13.2.10.7, “Correlated Subqueries”). Other possibilities for solving the problem are to use an uncorrelated subquery in the FROM clause or a LEFT JOIN.
Uncorrelated subquery:
SELECT s1.article, dealer, s1.price FROM shop s1 JOIN ( SELECT article, MAX(price) AS price FROM shop GROUP BY article) AS s2 ON s1.article = s2.article AND s1.price = s2.price;
LEFT JOIN:
SELECT s1.article, s1.dealer, s1.price FROM shop s1 LEFT JOIN shop s2 ON s1.article = s2.article AND s1.price < s2.price WHERE s2.article IS NULL;
The LEFT JOIN works on the basis that when s1.price is at its maximum value, there is no s2.price with a greater value and the s2 rows values will be NULL. See Section 13.2.9.2, “JOIN Syntax”.
sql – difference between natural join and inner join – Stack Overflow
One significant difference between INNER JOIN and NATURAL JOIN is the number of columns returned.
Consider:
TableA TableB
Column1 Column2 Column1 Column3
1 2 1 3The INNER JOIN of TableA and TableB on Column1 will return
a.column1 a.column2 b.column1 b.column3
1 2 1 3
SELECT * FROM TableA INNER JOIN TableB USING (Column1)
SELECT * FROM TableA INNER JOIN TableB ON TableA.Column1 = TableB.Column1The NATURAL JOIN of TableA and TableB on Column1 will return:
column1 column2 column3
1 2 3
SELECT * FROM TableA NATURAL JOIN TableBThe repeated column is avoided.
(AFAICT from the standard grammar, you can’t specify the joining columns in a natural join; the join is strictly name-based. See also Wikipedia.)
(There’s a cheat in the inner join output; the a. and b. parts would not be in the column names; you’d just have column1, column2, column1, column3 as the headings.)
Do AJAX requests retain PHP Session info? – Stack Overflow
The answer is yes:
Sessions are maintained server-side. As far as the server is concerned, there is no difference between an AJAX request and a regular page request. They are both HTTP requests, and they both contain cookie information in the header in the same way.
From the client side, the same cookies will always be sent to the server whether it’s a regular request or an AJAX request. The Javascript code does not need to do anything special or even to be aware of this happening, it just works the same as it does with regular requests.
ajax 를 이용한 경우에도 session 정보가 유지된다. 그러므로 이를 이용하여 사용자의 session을 확인하고 올바른 요청인지 server side에서 확인하는 과정이 요구된다.