Во-первых, вы можете использовать CTE для преобразования его в тип данных XML. Второй способ - через производную таблицу.
SQL
-- DDL and sample data population, start
DECLARE @tbl TABLE (SequentialNo INT PRIMARY KEY, Company VARCHAR(20), [DATA] VARCHAR(MAX));
INSERT INTO @tbl (SequentialNo, Company, [DATA])
VALUES
(1, 'ABC', '<ITEMS>
<ITEM>
<ID>1</ID>
<NAME>John</NAME>
</ITEM>
<ITEM>
<ID>5</ID>
<NAME>James</NAME>
</ITEM>
</ITEMS>');
-- DDL and sample data population, end
-- Method #1
-- CTE
;WITH rs AS
(
SELECT *, TRY_CAST([DATA] AS XML) AS [xmldata]
FROM @tbl
)
SELECT SequentialNo
, Company
, col.value('(ID/text())[1]','INT') AS ID
, col.value('(NAME/text())[1]','VARCHAR(40)') AS [Name]
FROM rs AS tbl
CROSS APPLY tbl.[xmldata].nodes('/ITEMS/ITEM') AS tab(col);
-- Method #2
-- Derived table
SELECT SequentialNo
, Company
, col.value('(ID/text())[1]','INT') AS ID
, col.value('(NAME/text())[1]','VARCHAR(40)') AS [Name]
FROM (SELECT *, TRY_CAST([DATA] AS XML) AS [xmldata]
FROM @tbl) AS tbl
CROSS APPLY tbl.[xmldata].nodes('/ITEMS/ITEM') AS tab(col);
Выход
+--------------+---------+----+-------+
| SequentialNo | Company | ID | Name |
+--------------+---------+----+-------+
| 1 | ABC | 1 | John |
| 1 | ABC | 5 | James |
+--------------+---------+----+-------+