将三个SQL Server表连接在一起以显示图像

Question

I am trying to create a Photo Album/Collection for each student in my ASP.NET website, using SQL Server tables.

Here are my table structure:

I want to store the image name within the Student_Images folder. Then each image will be linked to a Photo Collection. Each Photo Collection is linked to a group.

Then I want to display each group, any photo collections which are associated with that group, and then any images associated with that collection.

I have been able to display images related to each student, but I don't know how to add the 'Photo Collection' table between the Students and Images tables.

Here is how I would like it to display:

Here is how the tables would look populated:

Can anyone advise me as to how to go about making this connection?

Answer 1

Make some changes in your Photo_Collection table, create an FK within your Photo_Collection of Student_ID, then you'll be able to show the photo collection of all the students because through Student_ID, you can have access to student table as well as Student_Images. Hope it helps.

Answer 2

There's an idea of a foreign key - where a row in a table refers to a row in another table. You definitely want to do this for a number of reasons, to ensure data integrity and to document your relationships for whoever works on the site.

You don't quite have enough information to get where you want to get. You don't have any linkage between photo albums and the images they contain. You'll need another table for that.

I kinda recommend that you use column names that don't repeat the table name. You'll find you can then see patterns more clearly in your schema. For example Photo_Collection.Photo_Collection_Id should probably be just Photo_Collection.Id . It's more concise, and it's obvious which Id you're talking about because you always use the table name when referring to that column.

So, to get you nearer to where you need to be, I'd recommend something like this:

create table dbo.Students
(
  ID
    int not null identity( 1, 1 )
    constraint [Students.ID.PrimaryKey]
      primary key clustered,

  Name
    nvarchar( 50 ) --> not very generous :-)
)
go
create index [Students.Name.Index] on dbo.Students( Name ) --> maybe unique?
go

create table dbo.Student_Images
(
  ID
    int not null identity( 1, 1 )
    constraint [Student_Images.ID.PrimaryKey]
      primary key clustered,

  Student_ID
    int not null
    constraint [Student_Images.to.Student]
      foreign key references dbo.Students( ID )

  Filename
    nvarchar( 250 ) null,  --> null? really? each image should have a unique file name, dont you think?

  Description
    nvarchar( 250 ) null
)
go
create index [Student_Images.to.Students.Index] on dbo.Student_Images( Student_ID )
go

create table dbo.Photo_Collection
(
  ID
    int not null identity( 1, 1 )
    constraint [Photo_Collection.ID.PrimaryKey]
      primary key clustered,

  Name
    nvarchar( 250 ) null --> null? hmmm...could be hard to use
)
go
create index [Photo_Collection.Name.Index] on dbo.Photo_Collection( Name ) --> consider unique??
go

create table dbo.Photo_Collection_Images
(
  Photo_Collection_ID
    int not null
    constraint [Photo_Collection_Images.to.Photo_Collection]
      foreign key references dbo.Photo_Collection( ID ),

  Student_Image_ID
    int not null
    constraint [Photo_Collection_Images.to.Student_Images]
      foreign key references dbo.Student_Images( ID )
)

You didn't really describe your groups...and there are lots of questions still unanswered. For example, are Photo_Collections something that a student makes? If so, there should probably be a Student_ID in Photo_Collection with a foreign key to Students.

The table I added called Photo_Collection_Images relates your photo collections to the images. You'd include this table in any query that needs to display all the images in a given photo collection. I think that's the main missing bit for you. You'd do something similar for groups.

Also - FYI, pasting images of your text is kinda aggravating. Consider just pasting the text in and indenting it 4 spaces to get it to format correctly.

Edit :

To select, for example, all the images in a photo collection by student, you could do:

select
  pc.Name PhotoCollectionName,
  si.FileName FileName,
  si.Description FileDescription,
  s.Name StudentName
from
  dbo.Photo_Collection pc
  inner join
  dbo.Photo_Collection_Images pci
  on
    pc.Id = pci.Photo_Collection_ID
  inner join
  dbo.Student_Image si
  on
    pci.Student_Image_ID = si.ID
  inner join 
  dbo.Students s
  on 
    si.Student_Id = s.ID

This is pretty much the base query for everything.