DT_GUID to DT_WSTR yields braces around uniqueidentifier

I'm using a Lookup component to add a DT_GUID column named cat_id to a data flow, which is used in a downstream Derived Column component to add a DT_WSTR column named value. The DC expression simply casts the uniqueidentifier to the desired type: (DT_WSTR, 434)cat_id

But when the values are persisted in the destination table's nvarchar(434) column, they have braces around them, e.g. {F475DB7F-5CB0-4EE1-9BF2-758C77D7A6D7}

What is introducing those braces, and what do I need to do to prevent it?

You may remove the braces by using SUBSTRING function in the DC expression:
http://msdn2.microsoft.com/en-us/library/ms137541.aspx
SUBSTRING((DT_WSTR, 434)cat_id, 1, 40)

(if I remember GUID length, maybe the last param should be 39 or something like this).

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Michael Entin - MSFT wrote:

You may remove the braces by using SUBSTRING function in the DC expression:
http://msdn2.microsoft.com/en-us/library/ms137541.aspx

SUBSTRING((DT_WSTR, 434)cat_id, 1, 40)

(if I remember GUID length, maybe the last param should be 39 or something like this).

Thanks, but why is that even necesssary? In Transact SQL, when a uniqueidentifier is cast to a varchar/nvarchar the result doesn't have braces around the value.

|||It is very common to add braces around GUID representation, although it is of course unfortunate that SSIS implemented it differently than T-SQL.|||

Michael Entin - MSFT wrote:

It is very common to add braces around GUID representation, although it is of course unfortunate that SSIS implemented it differently than T-SQL.

Thanks for following up.

BTW, GUIDs are 36 characters and strings are 1-indexed, so the expression I'm using is:

SUBSTRING((DT_WSTR,434)cat_id,2,36)