DECLARE	@Sample TABLE
	(
		rowID INT IDENTITY(1, 1) PRIMARY KEY CLUSTERED,
		[xml] XML
	)

INSERT	@Sample
SELECT	'<stringList xmlns="http://schemas.myCompany.com/myProject/[app]/stringList/1.0"><value>value1</value></stringList>' UNION ALL
SELECT	NULL UNION ALL
SELECT	'<stringList xmlns="http://schemas.myCompany.com/myProject/[app]/stringList/1.0"><value>value5</value><value>value2</value></stringList>' UNION ALL
SELECT	'<stringList xmlns="http://schemas.myCompany.com/myProject/[app]/stringList/1.0"><value>value4</value><value>value1</value><value>value5</value><value>value2</value></stringList>'

SELECT	*
FROM	@Sample

;WITH XMLNAMESPACES('http://schemas.myCompany.com/myProject/[app]/stringList/1.0' AS theYak)
SELECT		myValue,
		COUNT(*) AS Items
FROM		(
			SELECT		t.c.value('.', 'VARCHAR(20)') AS myValue
			FROM		@Sample AS s
			CROSS APPLY	s.xml.nodes('/theYak:stringList/theYak:value') AS t(c)
		) AS d
GROUP BY	myValue