同样的sql在代码里跑比在sql里跑耗时久

Question

SELECT
count(*) as num
FROM mail_record202109
where create_time between '2021-09-20' and  '2021-09-28'
GROUP BY `to`

都是这段查询语句，sql里跑耗时1s不到
但是在springboot项目里跑，花了十几秒。为什么？