SQL学习--单表查询

指定列：select Sno,Sname from Student;

查询经过计算的值：select Sname, 'year of birth:', 2008-Sage, Sdept from student;

去除取值重复的行：select distinct Sno from student;

足条件的元组：select Sname,Sage from Student where Sdept ='CS' AND Sage<=19;

确定范围，集合 select Sname from Student where Sage BETWEEN 18 AND 20;

匹配查询 select * from Student where Sno LIKE '100%';

Order By子句 select Sno,Grade from SC where Cno ='2' ORDER　BY Grade DESC; //DESC是降序，缺省为升序

聚集函数：select COUNT(Sno) from Student;

Group By子句：select Cno,COUNT(Cno) from SC GROUP BY Cno;