uniqueidentifier

问题 I need to generate a unique code from a single PC, my software will be distribute by licence, and locally I need to identify the environment and send this code to the server. I don't want to mantain on the server a sequencial number and each client recieve a number of the sequence, i tried to read the MAC adress from NetworkInterfaces, but is not secure, the user can change easily the MAC adress. The best way I think if its possible to read the motherboard serial number, but I haven't found

问题 How to generate unique ID that is integer in java that not guess next number? 回答1: How unique does it need to be? If it's only unique within a process, then you can use an AtomicInteger and call incrementAndGet() each time you need a new value. 回答2: int uniqueId = 0; int getUniqueId() { return uniqueId++; } Add synchronized if you want it to be thread safe. 回答3: It's easy if you are somewhat constrained. If you have one thread, you just use uniqueID++; Be sure to store the current uniqueID

问题 If your ID column on a table is a unique identifier (Guid), is there any point creating a clustered primary key on the ID column? Given that they are globally unique, how would the sorting work? 回答1: GUIDs as they are are terrible for performance since they are effectively random values (this "breaks" clustered index), and they are awful for indexes, since less entries fit on a single page/extent (SQL Server terms). SQL Server 2005 introduces newsequentialid() which helps solving first

问题 If I were building a blog I could use the blog title as the unique identifier and parse it through the URL. However, what if I wanted to use numbers. You know how twitter has www.twitter.com/username/statuses/9834542? Has anyone figured out a nice way of making this work? using "_id" is out of the question since it's way too long. 回答1: As long as you can guarantee uniqueness, you're not constrained to using the default "_id" MongoDB supplies. Therefore, it's down to you how you generate this

问题 I'm new in NFC thing, so I tested several phones with calling getTagId() method in HCE mode, and this is the result: device | UID LG G2 | random LG G3 | static S4 | random HTC One Mini | static Xiaomi mi3 | static My questions: Why do some phones have static UID and some do not? Is this chipset related? Is it possible to get a fixed UID? I need it to authenticate the device. On other side, I'm using Kitkat CyanogenMod 11 on Xperia M, but I did not manage to use it for HCE, why? Any documents

问题 How are the Git commit IDs generated to uniquely identify the commits? Example: 521747298a3790fde1710f3aa2d03b55020575aa How does it work? Are they only unique for each project? Or for the Git repositories globally? 回答1: A Git commit ID is a SHA-1 hash of every important thing about the commit. I'm not going to list them all, but here's the important ones... The content, all of it, not just the diff. Commit date. Committer's name and email address. Log message. The ID of the previous commit(s

问题 This code doesn't work for MySQL 5.0, how to re-write it to make it work DELETE FROM posts where id=(SELECT id FROM posts GROUP BY id HAVING ( COUNT(id) > 1 )) I want to delete columns that dont have unique id. I will add that most of the time its only one id(I tried the in syntax and it doesnt work as well). 回答1: SELECT (sub)queries return result sets . So you need to use IN , not = in your WHERE clause. Additionally, as shown in this answer you cannot modify the same table from a subquery

问题 A table I have no control of the schema for, contains a column defined as varchar(50) which stores uniqueidentifiers in the format 'a89b1acd95016ae6b9c8aabb07da2010' (no hyphens) I want to convert these to uniqueidentifiers in SQL for passing to a .Net Guid. However, the following query lines don't work for me: select cast('a89b1acd95016ae6b9c8aabb07da2010' as uniqueidentifier) select convert(uniqueidentifier, 'a89b1acd95016ae6b9c8aabb07da2010') and result in: Msg 8169, Level 16, State 2,

问题 Today we received a feedback about our submission and we do not understand the reported problem: "Apps are not permitted to access the UDID and must not use the uniqueIdentifier method of UIDevice. Please update your apps and servers to associate users with the Vendor or Advertising identifiers introduced in iOS 6.". We know about the rejections about udid, but our App do not use this! After read this, our team reevaluated the App and we do not found occurrences from "UIDevice

问题 How can I get a devices unique ID in Swift? I need an ID to use in the database and as the API-key for my web service in my social app. Something to keep track of this devices daily use and limit its queries to the database. Thanks! 回答1: You can use this (Swift 3): UIDevice.current.identifierForVendor!.uuidString For older versions: UIDevice.currentDevice().identifierForVendor or if you want a string: UIDevice.currentDevice().identifierForVendor!.UUIDString There is no longer a way to