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SQL question HELP

SQL question HELP# Database - 数据库

h*t2099-11-01 07:11

1 楼

what is the averge of age among all students who participate in more than
2 activity
STUDENT (
StuID NUMBER,
LName VARCHAR2(12),
Fname VARCHAR2(12),
Age NUMBER,
Sex VARCHAR2(1),
Major NUMBER,
Advisor NUMBER,
city_code varchar2(3)
);
ACTIVITY (
actid number ,
activity_name varchar2(25))
PARTICIPATES_IN ;
create table PARTICIPATES_IN (
stuid number,
actid number )
thanks

s*i2099-11-01 07:11

2 楼

select AVG(Age)
from STUDENT,PARTICIPATES_IN
where STUDENT.StuID=PARTICIPATES_IN.StuID
having (select count(*)
from PARTICIPATES_IN
group by StuID)
>=2;

【在 h******t 的大作中提到】

: what is the averge of age among all students who participate in more than
: 2 activity
: STUDENT (
: StuID NUMBER,
: LName VARCHAR2(12),
: Fname VARCHAR2(12),
: Age NUMBER,
: Sex VARCHAR2(1),
: Major NUMBER,
: Advisor NUMBER,