Hi florenz,
You can refer below Stored Procedure where the checking is done whether GUID exists in database table or not.
You need to modify the SP according to you table structure
SQL
CREATE PROCEDURE [dbo].[CheckGUID]
@guid NVARCHAR(MAX)
AS
BEGIN
SET NOCOUNT ON;
IF NOT EXISTS(SELECT [GUID] FROM artificial WHERE [GUID] = @guid)
BEGIN
SELECT 'Not Exist'
END
ELSE
BEGIN
SELECT 'Exist'
END
END
END
You can refer below article for more detail on checking of existing record in database table.