SQL航空网的几个航班查询题：_sql 航班数据 求航线

                  表结构如下：
                  flight{flightID,StartCityID ,endCityID,StartTime}
                  city{cityID, CityName)
                  实验环境：
                  create table city(cityID int auto_increment primary
                  key,cityName varchar(20));
                  create table flight (flightID int auto_increment primary key,
                  StartCityID int references city(cityID),
                  endCityID int references city(cityID),
                  StartTime timestamp);
                  //航班本来应该没有日期部分才好，但是下面的题目当中涉及到了日期
                  insert into city values(null,'北京'),(null,'上海'),(null,'广州');
                  insert into flight values
                  (null,1,2,'9:37:23'),(null,1,3,'9:37:23'),(null,1,2,'10:37:23'),(null,2,3,'10:37:23');

                  1、查询起飞城市是北京的所有航班，按到达城市的名字排序

                  参与运算的列是我起码能够显示出来的那些列，但最终我不一定把它们显示出来。各个表组合出来的中间结果字段中必须包含所有运算的字段。
                  select * from flight f,city c
                  where f.endcityid = c.cityid and startcityid =
                  (select c1.cityid from city c1 where c1.cityname = "北京")
                  order by c.cityname asc;
                  mysql> select flight.flightid,'北京' startcity, e.cityname from
                  flight,city e wh
                  ere flight.endcityid=e.cityid and flight.startcityid=(select
                  cityid from city wh
                  ere cityname='北京');
                  mysql> select flight.flightid,s.cityname,e.cityname from
                  flight,city s,city e wh
                  ere flight.startcityid=s.cityid and s.cityname='北京' and
                  flight.endCityId=e.cit
                  yID order by e.cityName desc;

                  2、查询北京到上海的所有航班纪录（起飞城市，到达城市，起飞时间，航班号）
                  select c1.CityName,c2.CityName,f.StartTime,f.flightID
                  from city c1,city c2,flight f
                  where f.StartCityID=c1.cityID
                  and f.endCityID=c2.cityID
                  and c1.cityName='北京'
                  and c2.cityName='上海'
                  3、查询具体某一天（2005-5-8）的北京到上海的的航班次数
                  select count(*) from
                  (select c1.CityName,c2.CityName,f.StartTime,f.flightID
                  from city c1,city c2,flight f
                  where f.StartCityID=c1.cityID
                  and f.endCityID=c2.cityID
                  and c1.cityName='北京'
                  and c2.cityName='上海'
                  and 查帮助获得的某个日期处理函数(startTime) like '2005-5-8%'
                  mysql中提取日期部分进行比较的示例代码如下：
                  select * from flight where
                  date_format(starttime,'%Y-%m-%d')='1998-01-02'