Conversion failed when converting from a character string to uniqueidentifier I am creating a Dynamic CRM 2011 Report in SSRS.
I use several joins, And use GUID in joins.
For ex :

Quote.OpportunityId=Opprtunity.OpportunityId


The problem comes from parameters.
I have a parameter which its label is a name and the value is GUID of a record.
I retrieve them from a Dataset.
The query of the this Dataset(named siteDataset) is this :

select site.SiteId, site.Name from Site;


the siteId goes to the value of the parameter and site.name goes to the label of the parameter, the Parameter is named siteId itself.

But when I try to do this in another DataSet : 

siteGUIDInAnotherEntity='@siteId'


Give me the subject Error.
I even tried this :

CONVERT(VARCHAR(50), site.SiteId)


in siteId DataSet; But no success.

Any help will appreciated.
This may be a typo in your question, but just to be safe I'll post this as a possible answer - you shouldn't have those single quotes around @siteId, it should be like this:

siteGUIDInAnotherEntity=@siteId


The text string '@siteId' can't be converted into a uniqueidentifier for that join, and will result in the error you mentioned:

SELECT CAST('@siteId' AS uniqueidentifier);



  Msg 8169, Level 16, State 2, Line 1
  Conversion failed when converting from a character string to uniqueidentifier.