需要记忆的几个sql语句

链接查询：

1.查询两个表，在where中定义连接条件：

select student.sno,sname,ssex,sage,sdept,cno,grade.

from student,sc

where student.sno=sc.sno;

2.用Join在from中指定链接条件：

select student.sno,sname.ssex,sage,sdept,cno,grade

from student join sc on (student.sno=sc.sno)

3.比较复杂的查询条件

select student.sno,sname

from student.join sc on student.sno = sc.sno

where sc.cno='2' and sc.grade>90

4.多表查询：

select student.sno,sname,cname,grade

from student,sc,course

where student.sno  = sc.sno and sc.cno =course.cno;

5.查询选修了数据库系统原理课程的同学的学号和姓名和成绩：

select student.sno,sname,grade

from student,course,sc

where student.sno=sc.sno and course.cno = sc.cno and cname='数据库系统原理'