Попробуйте что-то вроде этого:
SELECT
Col1, Col2,
Section.value('(Name)[1]', 'VARCHAR(50)') AS 'Name',
Section.value('(SignedBy)[1]', 'VARCHAR(50)') AS 'SignedBy',
Section.value('(UserId)[1]', 'VARCHAR(50)') AS 'UserId',
Section.value('(Title)[1]', 'VARCHAR(50)') AS 'Title',
Section.value('(Status)[1]', 'VARCHAR(50)') AS 'Status',
Section.value('(LastModifiedOn)[1]', 'DATETIME') AS 'Last Modified On'
FROM
dbo.YourTable
CROSS APPLY
Col3.nodes('/SignatureSummary/SectionList/Section') AS Sig(Section)