;WITH MyCTE AS
(
SELECT *,
ROW_NUMBER()OVER (ORDER BY TextString) AS rn
FROM Table1
)
SELECT T1.TextString AS T1String,
T2.TextString AS T2String,
CASE WHEN T1.TextString = T2.TextString THEN T1.ID ELSE '' END AS NewCode,
CASE WHEN T1.TextString = T2.TextString THEN T2.ID ELSE '' END AS OldCode
FROM MyCTE T1
LEFT JOIN MyCTE T2
ON T1.rn = T2.rn+1
