FIRST_VALUE

Always returns a column from the first record within the partition.

SELECT 
	ColName1,
	ColName2,
	ColName3,
	FIRST_VALUE(ColName1) OVER (PARTITION BY ColName1 ORDER BY ColName1, ColName2) AS fv
FROM SchemaName.TableName
	ORDER BY ColName1, ColName2

Note: using PARTITION BY ColName1 is optional