CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CONSTRAINT **uc**_PersonID UNIQUE (P_Id,LastName)
)
答案 0 :(得分:3)
命名约束是绝对好的做法(否则SQL Server会使用随机名称命名它们,这使得使用常规升级脚本升级多个系统变得非常困难)。
最好使用前缀来查看这是什么类型的约束。
常见的是
最好将表的名称添加到约束中(以避免歧义)。在你的情况下,这是:
import UIKit
import CoreLocation
class HomeViewController: UIViewController, UIScrollViewDelegate ,UICollectionViewDataSource, UICollectionViewDelegate, CLLocationManagerDelegate {
// Location Manager
var locationManager: CLLocationManager = CLLocationManager()
//MARK: Location related functions
func trackLocation(){
// Set the delegate
self.locationManager.delegate = self
// Request location authorization
self.locationManager.requestWhenInUseAuthorization()
// Request a location update
if #available(iOS 9.0, *) {
self.locationManager.requestLocation()
} else {
// Fallback on earlier versions
}
// Start location updates
self.locationManager.startUpdatingLocation()
}
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
if let location = locations.first {
print("Found user's location: \(location)")
}
}
func locationManager(manager: CLLocationManager, didFailWithError error: NSError) {
print("Failed to find user's location: \(error.localizedDescription)")
}
Btw(命名约定):以单数形式使用表名(人而不是人)是很常见的。请在此处阅读:Table Naming Dilemma: Singular vs. Plural Names