SELECT  [name], 
AVG(a) as a, 
SUM(CASE WHEN b<=5 THEN 1 ELSE 0 END) * 100.0 / COUNT(b) AS b
FROM  ta
GROUP BY name
having 
AVG(a)>'1'

UNION ALL 
SELECT  '统计', 
AVG(a) as a,
AVG(b) as b
FROM(
SELECT  [name], 
AVG(a) as a, 
SUM(CASE WHEN b<=5 THEN 1 ELSE 0 END) * 100.0 / COUNT(b) AS b
FROM  ta
GROUP BY name
having 
AVG(a)>'1'
)ta

select * from ta
where name in
(
SELECT  [name]
FROM  ta
GROUP BY name
having 
AVG(a)>1
)