DECLARE @cols AS NVARCHAR(MAX),
@query  AS NVARCHAR(MAX)

SELECT @cols = STUFF((SELECT DISTINCT ',' +   QUOTENAME(ItemId) 
                    FROM CUSTOMER_ORDER
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

SELECT @query = 
'SELECT * FROM
(SELECT     
    CUSTOMER_NUMBER,
    ItemId, 
    1 as INTC
FROM CUSTOMER_ORDER)X
PIVOT 
(
    COUNT(INTC)
    for ItemId in (' + @cols + ')
) P'

EXEC SP_EXECUTESQL @query