I've corrected the SQL to include the schema name:

SELECT t.name AS [tname] ,

' update statistics ' + sch.name + '.[' + t.name + '] ' [comando]

FROM sys.tables t

INNER JOIN sys.schemas sch ON sch.schema_id = t.schema_id

LEFT JOIN sys.stats s ON t.object_id = s.object_id

JOIN ( SELECT object_id ,

SUM(rows) rows

FROM sys.partitions

GROUP BY object_id

HAVING SUM(rows) > 0

) pa ON t.object_id = pa.object_id

WHERE ( STATS_DATE(t.object_id, stats_id) IS NULL

OR DATEDIFF(DAY, STATS_DATE(t.object_id, stats_id), GETDATE()) >= 3

)

GROUP BY sch.name ,

t.name

ORDER BY 1