关于sqlite数据库连接查询问题?

Question

表1：如下CREATE TABLE student (sid integer, sname text, age integer);sqlite> select * from student;1|zhang|222|li|213|wang|194|xue|195|zhao|20表2：如下CREATE TABLE achievements (cid integer, sid integer, course text, results integer);2|1|shuxue|854|2|shuxue|906|3|shuxue|828|4|shuxue|7210|5|shuxue|100我要查询年龄为20的学生的成绩该怎么写连接sql语句？？？sqlite> select a.results from achievements as a inner join student as s where s.age=20;85908272100为什么上面的语句查出来的不是100这个数，而是把所有的成绩全打出来了？？正确的语句该怎么写？？？

Answer 1

少一个连接条件
select a.results from achievements as a inner join student as s where s.age=20;
改为
select a.results from achievements as a inner join student as s on a.sid = s.sid where s.age=20;