Guids, Unique Id's and Hashes

[Chris Dunaway]

I have used Guid's as a unique identifier in data applications. But in
a recent project, the length of the Guid's string is proving to be too
long. Is there a method for generating a unique string that is less
than the length of a Guid?

If I were to take the hash of a Guid string, what is the likelyhood
that two different Guids would have the same hash?

Can anyone offer any other suggestions?

Thanks

 

[Herfried K. Wagner [MVP]]

I have used Guid's as a unique identifier in data applications. But in
a recent project, the length of the Guid's string is proving to be too
long. Is there a method for generating a unique string that is less
than the length of a Guid?

I am curious what the max. number of characters for the identifier in the
scenario you describe is...

 

[Chris Dunaway]

At the moment, the length of the field is 30 characters, but the data
in it is in the following format (don't ask me why, I inherited this
code):

<custnum>-<uniqueid>-<city,state>

The entire string must be unique. The custnum, city, and state must
also be part of the string.

I can increase the size of the field, but I would then have to increase
the size of this same field in many other tables. I am hesitant to do
this unless I have to.

I was trying to determine a method to shorten the string.

Thanks

 

[Robin Tucker]

It's 8 bytes only - so I'm guessing if you aren't storing the GUID number,
but instead the actual decoded string, you will use up a tad more space

 

[Cor Ligthert]

Robin,

It's 8 bytes only - so I'm guessing if you aren't storing the GUID number,
but instead the actual decoded string, you will use up a tad more space

Are you sure of this and in my opinion serialized it will be more.

http://msdn.microsoft.com/library/d...n-us/cpref/html/frlrfsystemguidclasstopic.asp

Cor

 

[Herfried K. Wagner [MVP]]

It's 8 bytes only - so I'm guessing if you aren't storing the GUID number,
but instead the actual decoded string, you will use up a tad more space

GUIDs are 16 bytes...

 

[Robin Tucker]

My mistake, I didn't divide 128 bits by 8 correctly :/

 

[Robin Tucker]

Yes, what I meant to say was that, a guid being 16 bytes (ehem, excuse my
math) might look like this:


ABACACABACACBACD (128 bits = 16 bytes = 16 ASCII chars)



but stored as a string it will be bigger, like this:

00000118-0000-0000-C000-000000000046 (36 characters)