Question

首先，这是我的C＃代码，然后是存储过程。

public DataTable GetCourseHighPass(String tmpCourse)
{
    command.Connection = OpenConnection();

    try
    {
        command.CommandText = "exec GetCourseCompletions @tmpCourse = '" + tmpCourse + "'";
        SqlDataAdapter dataAdapter = new SqlDataAdapter(command);
        dataAdapter.Fill(dataTable);
        return dataTable;
    }
    catch (Exception)
    {
        throw new Exception("There are no VG's for this course.");
    }
    finally
    {
        command.Connection.Close();
    }
}

这是我的存储过程。

create procedure GetCourseCompletions
   @tmpCourse nvarchar(30)
as
   select (count(pnr) * 100 / (select count(pnr) 
                               from HasStudied  
                               where courseCode = @tmpCourse 
                                 and count(pnr) =)) as VGPrecentage 
   from HasStudied 
   where grade >= 5 
     and courseCode = @tmpCourse
go

问题在于，如果没有高通的学生，我会得到除以零的异常。寻找有关如何捕获此异常的建议，以便程序不会崩溃，甚至更好地重写存储过程，因此它首先不会出现异常。

感谢您的协助！

Answer 1

做埃里克说的话：

    DECLARE @count int
    Set @count = (select count(pnr) from HasStudied where courseCode = @tmpCourse and count(pnr) =...)
    IF @count = 0
    BEGIN
        SELECT 0 as VGPrecentage
    END
    ELSE
    BEGIN
        select (count(pnr)*100 / @count) as VGPrecentage from HasStudied where grade >= 5 and courseCode = @tmpCourse
    END

Answer 2

我建议你使用这种查询来代替那些处理 NULL 值和 Zero 值的查询：

SELECT 
    CASE WHEN part * total <> 0 THEN part * 100 / total ELSE 0 END
FROM (
    SELECT SUM(CASE WHEN grade > 5 THEN 1.00 ELSE 0.00 END) As part, SUM(1.00) as total
    FROM HasStudied
    WHERE courseCode = @tmpCourse) t

SQL Server＆amp; C＃存储过程＆amp;除以零例外

2 个答案: