SQL学习(一)

select B.kecheng, B.score, B.xuehao
from (select kecheng, max(score) AS score
　　from jiaScore
　　group by kecheng) A, jiaScore B
where A.kecheng = B.kecheng and A.score = B.score
A,B代表from后面的查询结果作为临时表、A，B为临时表的名字；
A.kecheng和B.kecheng代表查询结果集(临时表)中对应的字段；
说直接就是起别名、便于输入语句简单。
B.kecheng= jiaScore.kecheng
A.kecheng=(select kecheng , max(score) As score
　　from jiaScore
　　 group by kecheng).kecheng

SQL语句的书写顺序

• select
• from
• where
• group by
• having
• order by