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Can table columns with a Foreign Key be NULL?
...
Yes, you can enforce the constraint only when the value is not NULL. This can be easily tested with the following example:
CREATE DATABASE t;
USE t;
CREATE TABLE parent (id INT NOT NULL,
PRIMARY KEY (id)
) ENGINE=INNODB;
CREATE TABLE...
One-liner to check whether an iterator yields at least one element?
... iterator in case any_check ever needs to advance. This is worse than just converting the original iterator to a list.
– Rafał Dowgird
Mar 3 '11 at 8:54
1
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Round to 5 (or other number) in Python
...thon, but this works for me:
Python 2
def myround(x, base=5):
return int(base * round(float(x)/base))
Python3
def myround(x, base=5):
return base * round(x/base)
It is easy to see why the above works. You want to make sure that your number divided by 5 is an integer, correctly rounde...
What is the best way to find the users home directory in Java?
...\Application Data (CSIDL_LOCAL_APPDATA).
Sample JNA code:
public class PrintAppDataDir {
public static void main(String[] args) {
if (com.sun.jna.Platform.isWindows()) {
HWND hwndOwner = null;
int nFolder = Shell32.CSIDL_LOCAL_APPDATA;
HANDLE hToken...
Java: method to get position of a match in a String?
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The family of methods that does this are:
int indexOf(String str)
indexOf(String str, int fromIndex)
int lastIndexOf(String str)
lastIndexOf(String str, int fromIndex)
Returns the index within this string of the first (or last) occurrence of the specified ...
What are some uses of template template parameters?
...he exact type explicitly.
which you can use like this:
f<std::vector, int>(v); // v is of type std::vector<int> using any allocator
or better yet, we can just use:
f(v); // everything is deduced, f can deal with a vector of any type!
UPDATE: Even this contrived example, while illu...
Error: allowDefinition='MachineToApplication' beyond application level
...
I opened the website in IIS manager
right clicked the WCF folder
clicked Convert to Application
and then submitted with Ok
WCF is back and running.
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Concatenating null strings in Java [duplicate]
...ly reference values need to be considered. If the reference is null, it is converted to the string "null" (four ASCII characters n, u, l, l). Otherwise, the conversion is performed as if by an invocation of the toString method of the referenced object with no arguments; but if the result of invoking...
Getting View's coordinates relative to the root layout
...swers. One claims to be faster, and another claims to be easier.
private int getRelativeLeft(View myView) {
if (myView.getParent() == myView.getRootView())
return myView.getLeft();
else
return myView.getLeft() + getRelativeLeft((View) myView.getParent());
}
private int get...
Which, if any, C++ compilers do tail-recursion optimization?
... done for more than a decade), even for mutually recursive calls such as:
int bar(int, int);
int foo(int n, int acc) {
return (n == 0) ? acc : bar(n - 1, acc + 2);
}
int bar(int n, int acc) {
return (n == 0) ? acc : foo(n - 1, acc + 1);
}
Letting the compiler do the optimisation is stra...