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I want to generate 10 digit unique number, i have tried with date and time but it goes arround 14 digit. so please tell me how can i generate 10 digit unique number. Even if i restart the application it should maintain the uniqueness in the new generated number.
I can able to generate the 14 digit unique number. Is possible to scale down this 14 digit number into 10 digit unique number ?
Updated 18-May-11 22:56pm
Niklas L 18-May-11 8:24am    
Your question makes no sense. Unique compared to what? Start with 1000000000 and add 1 each time. That will give you all possible ten digit unique numbers. (A 32 bit representation is not enough, so pick a 64 bit integer.)
LaxmikantYadav 18-May-11 8:51am    
In this solution i have stored last number. And after generation of new number again have to update the last stored number which is not fixible. I want to generate number like using datetime but i want it upto 10 digit.
I think Niklas Lindquist given a easy solution. you will have only one 10 digit number and whenever you want to generate a number just increment it as uniqueNumber++;There is no need of updating last number.
LaxmikantYadav 18-May-11 9:43am    
Suppose i generate 10 number using niklas's logic and exit from application then on next run how can i generate unique number without storing previous unique number.
this is the real requirement. This has to be mentioned in your question.So the requirement is that you have to generate a 10 digit unique number,Like a roll number for a student,right.

This might help a little: Link[^]

The post describes the GUID generation algorithm and how it can be modified for specific situations to be shorter. Interesting read.
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fjdiewornncalwe 19-May-11 10:47am    
It is indeed an interesting read. Great find. +5
LaxmikantYadav 26-May-11 0:39am    
Guid is so long, I want upto 10 digit long.
tolw 26-May-11 3:51am    
That's why i suggested READING the article I linked to and NOT using GUID. At the end of the article there is a real live example of how to create your own guid-like id which can be shorter then the real guid, but has some specific limitations.
Look at the below link. This may help you[^]

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LaxmikantYadav 18-May-11 8:47am    
Guid is so long in size, I want upto 10 digit long.
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Sergey Alexandrovich Kryukov 18-May-11 15:45pm    
This is good, but only if request stay apart in couple of milliseconds or so.
I don't think using a combination of date and time is the right one, since the smallest unit you can get is millisecond.

I would go with GUID. But if you insist that it has to be done with time, than I think a combination of GetTickCount[^] (beware of its 49.7 days limitation or better GetTickCount64[^]) and a rand()[^] would be sufficient.
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Sergey Alexandrovich Kryukov 18-May-11 15:45pm    
GUID is not 100% guarantee.
Stephen Wiria 18-May-11 19:11pm    
True, I believe unique here means practically unique.
But then again, I don't think he could get a better and easier solution than GUID
LaxmikantYadav 19-May-11 0:17am    
GUID is greater than 10 digit. and if i use GetTickCount it is fine for first time. once i restart the pc it will again give me the same number. so uniqueness of the numbers can not be maintain.
Stephen Wiria 19-May-11 1:51am    
Yes, GetTickCount gives system uptime in milliseconds.
Right now, I can't give you better solution other than GUID. Sorry.
Dim RandomNumber As Integer
RandomNumber = RandomClass.Next(999999999,9999999999)
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LaxmikantYadav 18-May-11 8:52am    
I want in C++, And in this way we cant maintain the uniqueness of numbers.

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