Question

我正在尝试做一些简单的事情，但未能在SQL中应用。基本上，我有两个表 - 一个叫做CarHires，它只包含三列 - CarID，StartDate（当租车时）和EndDate（当车返回时）。和日期维度 - DimDate。

我想要实现的是计算每天租用的汽车数量。

这是SQL Fiddle我嘲笑让事情变得简单。

答案应该如下：

public partial class MyDBContext : IdentityDbContext<ApplicationUser>
{
    public FunkaDbContext()
        : base("name=MyDBContext", throwIfV1Schema: false)
    {
        Database.SetInitializer<MyDBContext>(new DropCreateDatabaseIfModelChanges<MyDBContext>());
    }

    public virtual DbSet<educationSignup> EducationSignups { get; set; }
    public virtual DbSet<ParticipantsInformation> ParticipantsInformations { get; set; }
    public virtual DbSet<PaymentInformation> PaymentInformations { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

        modelBuilder.Entity<educationSignup>()
            .HasMany(e => e.participantsInformations)
            .WithRequired(e => e.educationSignup)
            .HasForeignKey(e => e.SignupId)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<educationSignup>()
            .HasMany(e => e.paymentInformations)
            .WithRequired(e => e.educationSignup)
            .HasForeignKey(e => e.SignupId)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<IdentityUser>().HasKey<string>(u => u.Id);
        modelBuilder.Entity<IdentityRole>().HasKey<string>(r => r.Id);
        modelBuilder.Entity<IdentityUserRole>().HasKey(r => new { r.RoleId, r.UserId });
    }

    public static MyDbContext Create()
    {
        return new MyDbContext();
    }
}

非常感谢任何帮助！

Answer 1

这有效：

SELECT  D.Fulldate,
        ISNULL(COUNT(*),0) AS NumberofCars
FROM DimDate D
LEFT JOIN CarHires C
  ON D.Fulldate BETWEEN C.Startdate AND C.Enddate
GROUP BY D.Fulldate
ORDER BY D.Fulldate;

Answer 2

您根据startDate错误地加入了DimDate和CarHires，不需要full inner join：

select dimdate.Fulldate,
COUNT(CarID) AS NumberofCars   
FROM DimDate, CarHires     
WHERE dimdate.Fulldate BETWEEN CarHires.Startdate AND CarHires.Enddate    
GROUP BY dimdate.Fulldate

日期之间的SQL计数

2 个答案: