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Add Foreign Key to existing table
...
To add a foreign key (grade_id) to an existing table (users), follow the following steps:
ALTER TABLE users ADD grade_id SMALLINT UNSIGNED NOT NULL DEFAULT 0;
ALTER TABLE users ADD CONSTRAINT fk_grade_id FOREIGN KEY (grade_id) REFERENCES grades(id);
...
MySQL - SELECT WHERE field IN (subquery) - Extremely slow why?
...NNER JOIN sometable st2 ON (st1.relevant_field = st2.relevant_field)
GROUP BY st1.id /* list a unique sometable field here*/
HAVING COUNT(*) > 1
I think st2.relevant_field must be in the select, because otherwise the having clause will give an error, but I'm not 100% sure
Never use IN with a ...
Is it possible to append to innerHTML without destroying descendants' event listeners?
...use DOM functions:
function start() {
var myspan = document.getElementById("myspan");
myspan.onclick = function() { alert ("hi"); };
var mydiv = document.getElementById("mydiv");
mydiv.appendChild(document.createTextNode("bar"));
}
Edit: Bob's solution, from the comments. Post y...
Align image in center and middle within div
...art.net/fs71/200H/f/2013/236/d/b/bw_avlonas_a5_beach_isles_wallpaper_image_by_lemnosexplorer-d6jh3i7.jpg" />
</div>
CSS
*
{
padding: 0;
margin: 0;
}
#over
{
position:absolute;
width:100%;
height:100%;
text-align: center; /*handles the horizontal centering*/
}
/*ha...
How to check if an int is a null
...er to be able to be null, you need to use Integer instead of int.
Integer id;
String name;
public Integer getId() { return id; }
Besides the statement if(person.equals(null)) can't be true, because if person is null, then a NullPointerException will be thrown. So the correct expression is if (pe...
how to break the _.each function in underscore.js
...s the native forEach method's behavior, and the native forEach doesn't provide to escape the loop (other than throwing an exception).
However, all hope is not lost! You can use the Array.every method. :)
From that link:
every executes the provided callback function once for each element presen...
Labels for radio buttons in rails form
... imageUploader: {
brandingHtml: "Powered by \u003ca href=\"https://imgur.com/\"\u003e\u003csvg class=\"svg-icon\" width=\"50\" height=\"18\" viewBox=\"0 0 50 18\" fill=\"none\" xmlns=\"http://www.w3.org/2000/svg\"\u003e\u003cpath d=\"M46.1709 9.17788C46.1709 8.26454...
What is the best way to prevent session hijacking?
...mited time physical access to a filesystem. Imagine a laptop left unlocked by a colleague rushing to the toilet, now all I need to do is to go to that laptop, install EditThisCookie plugin, grab his cookies at plus.google.com using EditThisCookie export feature and now I have his account. Time taken...
怎么往SetTimer的回调函数传递参数 - C/C++ - 清泛网 - 专注C/C++及内核技术
...Proc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
HDC hdc;
switch (message)//message就是消息号
{
case WM_COMMAND:
...
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;...
Difference between dict.clear() and assigning {} in Python
...o not destroy the removed object in the dict which may still be referenced by someone else.
– Lorenzo Belli
Jan 26 '17 at 10:09
...