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Remove Primary Key in MySQL
...
Without an index, maintaining an autoincrement column becomes too expensive, that's why MySQL requires an autoincrement column to be a leftmost part of an index.
You should remove the autoincrement property before dropping the key:
ALTER TABLE...
How do I create a unique constraint that also allows nulls?
...R TABLE dbo.Party ADD SamAccountNameUnique
AS (Coalesce(SamAccountName, Convert(varchar(11), PartyID)))
ALTER TABLE dbo.Party ADD CONSTRAINT UQ_Party_SamAccountName
UNIQUE (SamAccountNameUnique)
You simply have to put something in the computed column that will be guaranteed unique across the...
How to map a composite key with JPA and Hibernate?
...inner class):
public class TimePK implements Serializable {
protected Integer levelStation;
protected Integer confPathID;
public TimePK() {}
public TimePK(Integer levelStation, Integer confPathID) {
this.levelStation = levelStation;
this.confPathID = confPathID;
...
How do you trigger a block after a delay, like -performSelector:withObject:afterDelay:?
... using performSelector:withObject:afterDelay: but with an argument like int / double / float ?
19 Answers
...
Swift variable decorations with “?” (question mark) and “!” (exclamation mark)
...u don't check for nil you'll get a runtime error)
// Cannot be nil
var x: Int = 1
// The type here is not "Int", it's "Optional Int"
var y: Int? = 2
// The type here is "Implicitly Unwrapped Optional Int"
var z: Int! = 3
Usage:
// you can add x and z
x + z == 4
// ...but not x and y, because ...
Objective-C: Property / instance variable in category
...
.h-file
@interface NSObject (LaserUnicorn)
@property (nonatomic, strong) LaserUnicorn *laserUnicorn;
@end
.m-file
#import <objc/runtime.h>
static void * LaserUnicornPropertyKey = &LaserUnicornPropertyKey;
@implementat...
Constructors in Go
... have a struct like this :
type Thing struct {
Name string
Num int
}
then, if the zero values aren't fitting, you would typically construct an instance with a NewThing function returning a pointer :
func NewThing(someParameter string) *Thing {
p := new(Thing)
p.Name = somePara...
How do you create a Swift Date object?
... Time in Swift
In Swift, dates and times are stored in a 64-bit floating point number measuring the number of seconds since the reference date of January 1, 2001 at 00:00:00 UTC. This is expressed in the Date structure. The following would give you the current date and time:
let currentDateTime = Da...
Real mouse position in canvas [duplicate]
...lient window you'll have to subtract the position of the canvas element to convert it relative to the element itself.
Example of integration in your code:
//put this outside the event loop..
var canvas = document.getElementById("imgCanvas");
var context = canvas.getContext("2d");
function draw(ev...
How to render a PDF file in Android
...rer(getSeekableFileDescriptor());
// let us just render all pages
final int pageCount = renderer.getPageCount();
for (int i = 0; i < pageCount; i++) {
Page page = renderer.openPage(i);
// say we render for showing on the screen
page.render(mBitmap, null, null, Page.RENDER_MODE...