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SQL JOIN - WHERE clause vs. ON clause
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@JamesHutchison It's tough to make reliable performance generalizations based on observed behaviors like this. What was true one day tends to be wrong the next, because this is an implementation detail rather than documented behavior. Database teams are always look...
How to check for an active Internet connection on iOS or macOS?
...y via closures
let reachability = Reachability()!
reachability.whenReachable = { reachability in
if reachability.connection == .wifi {
print("Reachable via WiFi")
} else {
print("Reachable via Cellular")
}
}
reachability.whenUnreachable = { _ in
print("Not reachabl...
How to iterate through a DataTable
I need to iterate through a DataTable . I have an column there named ImagePath .
4 Answers
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VC的陷阱，看哪些条款会威胁到创业者的利益 - 资讯 - 清泛网 - 专注C/C++及内核技术
...掉，你会发现当初的高估值完全没有意义，你手里的股票无法兑到那么多的现金。
第二，你的估值实在夸张，导致后续轮次的融资难以进行。假如你在天使轮拿到了一亿元的估值，到了 A 轮还有哪个资方能够继续抬高估值投你...
Easiest way to detect Internet connection on iOS?
...through HTTPUrlConnection instantly fail if there is no connection available. This seems like completely sane behavior, and I was surprised to find NSURLConnection in iOS did not emulate it.
...
廉价共享存储解决方案2-drbd+cman+gfs2 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...t -t gfs2 /dev/drbd0 /gfs
节点1
节点2
4、测试
居然无法访问
Cman 服务器居然无法重启。
强行关机重启之后先查看状态，然后提升为主节点，第二台机器同样操作，
然后分别启动cman ,接着分别挂载。 gfs_controld 没...
动态追踪（Dynamic Tracing）技术漫谈 - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...大部分问题其实是线上才有的问题，很难复现，或者几乎无法复现。而有些问题出现的比率又很小，只有百分之一、千分之一，甚至更低。我们最好能够不用摘机器下线，不用修改我们的代码或者配置，不用重启服务，在系统还...
Android中Java和JavaScript交互 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...用，因此onReceiveValue也执行在主线程。
疑问解答
Alert无法弹出
你应该是没有设置WebChromeClient,按照以下代码设置：
myWebView.setWebChromeClient(new WebChromeClient() {});
Uncaught ReferenceError: functionName is not defined
问题出现原因，网页的j...
How to use android emulator for testing bluetooth application?
...er settings of the virtual machine, Goto serialports -> Port 1 check Enable serial port select a port number
then select port mode as disconnected click ok. now, start virtual
machine. Under Devices -> USB Devices -> you can find your laptop
bluetooth listed. You can simply check t...
Error 908: Permission RECEIVE_SMS has been denied. - App Inventor 2 中...
...其他所有版本的Companion都是从它派生而来的。然而，我们无法通过Play商店分发它（正如我所提到的，我们申请了豁免权，但被拒绝了），所以我们只通过网站分发它。“u”版本的伴侣允许对使用谷歌认为可疑的功能的应用程序...