sql查询以基于特定列填充具有多个数据表的数据集

Question

I have a SQL Server table called tSongList that contains the following information:

colAlbumID, colSongName, colAlbumTrackNumber, colRequestedCount, colPlayPriority

The purpose of this table is to help a DJ keep a list of which songs the DJ should play and which album they are from. I have a C# class that will take a list of songs from a specific albumID and calculate the colPlayPriority based on the colRequestedCount . I have designed this class to take a DataTable containing the columns above and compute the necessary information.

So my question is if I want to use SQL to select all the rows from the tSongList , how do I get the SQL result into multiple DataTables grouped by colAlbumID ? In other words, I want a DataTable for each Album that contains it's song information.

I know that I can use a SqlDataAdapter to fill a DataSet and since a DataSet can contain multiple DataTables , is there a way to construct a SQL query to return a DataSet containing the DataTables grouped by albumID ?

Also if this can't be done, should I just select everything into one DataTable and use the Select function to get a DataRow array instead?

Answer 1

One option is to return a single DataTable and use LINQ to create your grouping.

var albumGroups = from a in dtAlbums.AsEnumerable()
  group a by a.Field<int>("albumID") into g
  select new { colSongName = g.Field<string>("colSongName"), 
               colAlbumTrackNumber = g.Field<int>("colAlbumTrackNumber"),
               colRequestedCount = g.Field<int>("colRequestedCount"),
               colPlayPriority = g.Field<int>("colPlayPriority") };

Answer 2

I think the example on MSDN will show you how to do this. You will make life much easier for yourself if you properly normalise your data first. You can create a hierarchical DataSet with the necessary relationships in place making it trivial to get all songs for an album.