（参考）数据库设计与查询优化

m SC1 SC1 y o =( o from Course1 ame =' 数据库') )o =( o from Course1 ame =' 数据库') (1) 将选修了数据库课程的学生成绩加 5 分。 update SC1 set Grade = Grade +5 o in ( o from Course1 ame =' 数据库') 第 9页共 65页天津理工大学教务处制表 select Grade from SC1 o in ( o from Course1 ame =' 数据库') (2) 将计算机系选修了 2 号课程的学生成绩置 0。 update SC1 set Grade =0 o = '2' and Sno in( select Sno from Student11 where Sdept =' 计算机') o , Grade from SC 1 o = '2' and Sno in( select Sno from Student 1 where Sdept =' 计算机') 第 10页共 65页天津理工大学教务处制表(3) 将王 0 的数据库成绩改为 85。 update SC 1 set Grade = 85 o in( o from Course 1 ame =' 数据库') and Sno in( select Sno from Student 1 where Sname =' 王0' ) select Grade from SC1 o in( o from Course1 ame =' 数据库') and Sno in( select Sno from Student1 where Sname ='王') (4) 将选修了 2 号课程且成绩为空的选课记录删除。 delete from SC1 o = '2' and Grade is null;