What is the string length of a GUID?

 

I want to create a varchar column in SQL that should contain N'guid' while guid is a generated GUID by .NET (Guid.NewGuid) - class System.Guid.

What is the length of the varchar I should expect from a GUID? Is it a static length?

Should I use nvarchar (will GUID ever use Unicode characters)? 

varchar(Guid.Length)

PS. I don't want to use a SQL row guid data-type. I am just asking what is Guid.MaxLength .

It depends on how you format the Guid:

  • Guid.NewGuid().ToString() => 36 characters (Hyphenated)
    outputs: 12345678-1234-1234-1234-123456789abc

  • Guid.NewGuid().ToString("D") => 36 characters (Hyphenated, same as ToString() )
    outputs: 12345678-1234-1234-1234-123456789abc

  • Guid.NewGuid().ToString("N") => 32 characters (Digits only)
    outputs: 12345678123412341234123456789abc

  • Guid.NewGuid().ToString("B") => 38 characters (Braces)
    outputs: {12345678-1234-1234-1234-123456789abc}

  • Guid.NewGuid().ToString("P") => 38 characters (Parentheses)
    outputs: (12345678-1234-1234-1234-123456789abc)

  • Guid.NewGuid().ToString("X") => 68 characters (Hexadecimal)
    outputs: {0x12345678,0x1234,0x1234,{0x12,0x34,0x12,0x34,0x56,0x78,0x9a,0xbc}}

    • 36, and the GUID will only use 0-9A-F (hexidecimal!).

    12345678-1234-1234-1234-123456789012

    That's 36 characters in any GUID--they are of constant length. You can read a bit more about the intricacies of GUIDs here.

    You will need two more in length if you want to store the braces.

    Note: 36 is the string length with the dashes in between. They are actually 16-byte numbers.

    The correct thing to do here is to store it as uniqueidentifier - this is then fully indexable, etc. at the database. The next-best option would be a binary(16) column: standard GUIDs are exactly 16 bytes in length.

    If you must store it as a string, the length really comes down to how you choose to encode it. As hex (AKA base-16 encoding) without hyphens it would be 32 characters (two hex digits per byte), so char(32) .

    However, you might want to store the hyphens. If you are short on space, but your database doesn't support blobs / guids natively, you could use Base64 encoding and remove the == padding suffix; that gives you 22 characters, so char(22) . There is no need to use Unicode, and no need for variable-length - so nvarchar(max) would be a bad choice, for example.

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