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Using ASCII encoding, how many characters are there in a GUID?
I'm interested in the Microsoft style, which includes the curly brackets and dashes.
725
That's 36 characters in any GUID--they are of constant length. You can read a bit more about the intricacies of GUIDs here.
The GUID data type is a text string representing a Class identifier (ID). COM must be able to convert the string to a valid Class ID. All GUIDs must be authored in uppercase. The valid format for a GUID is {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} where X is a hex digit (0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F).
The GUID generation algorithm relies on the fact that it has all 16 bytes to use to establish uniqueness, and if you throw away half of it, you lose the uniqueness. There are multiple GUID generation algorithms, but I'll pick one of them for concreteness, specifically the version described in this Internet draft.
The globally unique identifier (GUID) data type in SQL Server is represented by the uniqueidentifier data type, which stores a 16-byte binary value. A GUID is a binary number, and its main use is as an identifier that must be unique in a network that has many computers at many sites.
From MSDN:
A GUID is a 128-bit value consisting of one group of 8 hexadecimal digits, followed by three groups of 4 hexadecimal digits each, followed by one group of 12 hexadecimal digits. The following example GUID shows the groupings of hexadecimal digits in a GUID: 6B29FC40-CA47-1067-B31D-00DD010662DA
From Wikipedia:
Often braces are added to enclose the above format, as such:
{3F2504E0-4F89-11D3-9A0C-0305E82C3301}
So a total of 38 characters in the typical hexadecimal encoding with curly braces.
-Adam
115
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