//查询某一天的systolic_pressure字段的平均值。
DB::query(
"select avg(systolic_pressure) as systolic,avg(diastolic_pressure) as diastolic from mk_xueya where uid="
.
$_G
[uid].
" and date_format(addtime,'%Y%m%e')="
date
(Ym).
$day
);