Q1.有一个学生表student,字段分别有自增主键id,学生名称name,分数score,记录时间rowdate
1)用一条语句,把及格(score>60)的记录的score改成1,把不及格的score都改成0,注意只能用一条语句
2)把学生名字重复的记录删除掉,每个名字只保留一条记录
Q2.
public myclass
{
public static int num=1;
public static myclass()
{
Console.WriteLine(++num);
}
public myclass()
{
Console.WriteLine(++num);
}
}myclass a=new myclass();
myclass b=new myclass();
结果输出什么?
1)用一条语句,把及格(score>60)的记录的score改成1,把不及格的score都改成0,注意只能用一条语句
2)把学生名字重复的记录删除掉,每个名字只保留一条记录
Q2.
public myclass
{
public static int num=1;
public static myclass()
{
Console.WriteLine(++num);
}
public myclass()
{
Console.WriteLine(++num);
}
}myclass a=new myclass();
myclass b=new myclass();
结果输出什么?
1.Update s set s.score = case when s1.score > 60 then 1 else 0 end
from Student s
inner join Student s1 on s1.id = s.id
2.Delete student
where id not in
(
select max(id) from student group by name
)
Q2:
执行步骤:
==> myclass a=new myclass();
==> num =1
==> public static myclass() ++num num = 2; (writeLine)
==> public myclass() ++num num=3; (writeLine)
==> myclass b=new myclass();
==> public myclass() ++num; num=4; (writeLine)Result:
2
3
4
Q2,代码有问题.public myclass ? ==> public class myclasspublic static myclass() ? ==> static myclass()
inner join Student s1 on s1.id = s.id <== 这个完全没必要,呵呵
2.delete test where id not in (select max(id) from test group by name)
Q2.
2
3
4
对头,题目都有错误啦public static myclass() 应该去掉public
结果是
2
3
4