JDBC编程--SQL基础

● 现在有一个学生表,一个课程成绩表,请问,怎么找出学生课程的最高分数,谈一谈思路

无答案

● 现在,有一个组合索引(A,B,C),可以有哪几种查询方式?

考察点:sql语句

参考回答:

优: select * from test where a=10 and b>50

差: select * from test where b = 50

 

优: select * from test order by a

差: select * from test order by b

差: select * from test order by c

 

优: select * from test where a=10 order by a

优: select * from test where a=10 order by b

差: select * from test where a=10 order by c

 

优: select * from test where a>10 order by a

差: select * from test where a>10 order by b

差: select * from test where a>10 order by c

 

优: select * from test where a=10 and b=10 order by a

优: select * from test where a=10 and b=10 order by b

优: select * from test where a=10 and b=10 order by c

 

优: select * from test where a=10 and b=10 order by a

优: select * from test where a=10 and b>10 order by b

差: select * from test where a=10 and b>10 order by c

● 写SQL:找出每个城市的最新一条记录。

考察点:sql语句

参考回答:

id 城市 人口 信息 创建时间
1 北京 100 info1 时间戳
2 北京 100 info2 时间戳
3 上海 100 info3 时间戳
4 上海 100 info4 时间戳

posted @ 2019-05-08 21:58  IT刑天  阅读(396)  评论(0编辑  收藏  举报