SELECT year, "一季度" as 季度,Avg(total) AS avgtotal
FROM tb
where month in(1,2,3)
GROUP BY year
union
SELECT year, "二季度" ,Avg(total)
FROM tb
where month in (4,5,6)
GROUP BY year
union
SELECT year, "三季度" as 季度,Avg(total)
FROM tb
where month in (7,8,9)
GROUP BY year
UNION
SELECT year, "四季度" ,Avg(total)
FROM tb
where month in (10,11,12)
GROUP BY year ORDER BY year