alter table sc
add GPA float;               --加入绩点列
alter table sc
add number int identity(1,1);--将表按原始位置顺序编号（可加可不加）
alter table sc add primary key(number)
declare score_visit cursor    --声明一个游标      
for select score from sc 
open score_visit              --打开游标  
declare @GPA float
select @GPA=score from sc
fetch next from score_visit into @GPA
while @@fetch_status=0        --循环读取
begin
if @GPA>=90
update sc set GPA=4.0 where current of score_visit;
if @GPA >=85 and @GPA <90
update sc set GPA =3.7 where current of score_visit;
if @GPA >=82 and @GPA <85
update sc set GPA =3.3 where current of score_visit;
if @GPA >=78 and @GPA <81
update sc set GPA =3.0 where current of score_visit;
if @GPA >=75 and @GPA <78
update sc set GPA =2.7 where current of score_visit;
if @GPA >=72 and @GPA <75
update sc set GPA =2.3 where current of score_visit;
if @GPA >=68 and @GPA <72
update sc set GPA =2.0 where current of score_visit;
if @GPA >=64 and @GPA <68
update sc set GPA =1.5 where current of score_visit;
if @GPA >=60 and @GPA <64
update sc set GPA =1.0 where current of score_visit;
if @GPA <60
update sc set GPA =0 where current of score_visit;
fetch next from score_visit into @GPA
end
close score_visit              --关闭游标
deallocate score_visit         --删除游标