If you look at the values involved (in pairs) of hex digits you can see that the last 7 bytes are the same in both cases, but the first 9 are switched around a bit. Going from your example, but rewriting each pair in the .NET as 00, 11, 22 etc and switching the relevant … Read more
You can use the SYS_GUID() function to generate a GUID in your insert statement: insert into mytable (guid_col, data) values (sys_guid(), ‘xxx’); The preferred datatype for storing GUIDs is RAW(16). As Gopinath answer: select sys_guid() from dual union all select sys_guid() from dual union all select sys_guid() from dual You get 88FDC68C75DDF955E040449808B55601 88FDC68C75DEF955E040449808B55601 88FDC68C75DFF955E040449808B55601 As … Read more
in my case most ids will be generated within a large number of mobile clients, not within a limited set of servers. I wonder if in this case, there is a justified concern. That sounds like very bad architecture to me. Are you using a two-tier architecture? Why would the mobile clients have direct access … Read more
A clustered index on GUID is not a good design. The very nature of GUID is that it’s random, while a clustered index physically orders the records by the key. The two things are completely at odds. For every insert SQL has to reorder the records on disk! Remove clustering from this index! The time … Read more
Kimberley Tripp (SQLSkills.com) has an article on using GUID’s as primary keys. She advices against it because of the unnecessary overhead.
You can try the following: function GUID() { if (function_exists(‘com_create_guid’) === true) { return trim(com_create_guid(), ‘{}’); } return sprintf(‘%04X%04X-%04X-%04X-%04X-%04X%04X%04X’, mt_rand(0, 65535), mt_rand(0, 65535), mt_rand(0, 65535), mt_rand(16384, 20479), mt_rand(32768, 49151), mt_rand(0, 65535), mt_rand(0, 65535), mt_rand(0, 65535)); } Source – com_create_guid
UUIDs/GUIDs are specified by RFC4122. Although Version 4 UUIDs are created from random numbers Section 6 makes an explicit statement on security: Do not assume that UUIDs are hard to guess; they should not be used as security capabilities (identifiers whose mere possession grants access), for example. A predictable random number source will exacerbate the … Read more
Updated Answer This is now something you can do natively in JavaScript/TypeScript with crypto.randomUUID(). Here’s an example generating 20 UUIDs. for (let i = 0; i < 20; i++) { let id = crypto.randomUUID(); console.log(id); } Original Answer There is an implementation in my TypeScript utilities based on JavaScript GUID generators. Here is the code: … Read more
Why worry about defaults for Guid columns in the database at all? Why not just generate the Guid on the client like any other value. That requires you have a method in your client code that will generate COMB-like guids: public static Guid NewGuid() { var guidBinary = new byte[16]; Array.Copy( Guid.NewGuid().ToByteArray(), 0, guidBinary, 0, … Read more
Could you not just store the .Net Guid as a string and read it into Java? That way you don’t need to worry about byte order or anything. If not then This explains how the bytes are laid out in C# http://msdn.microsoft.com/en-us/library/fx22893a.aspx