Inner select on one to many

Hi all,

I have 2 tables event + event_artist

event
eventId | eventName
1 , gig1
2, gig2

event_artist
eventId, artistName
1, Led Zip
1, The Beatles

ie Led Zep and the Beatles are both playing @ Gig1

I need to create the SQl to bind to a gridview ( you necessarily need to know about gridviews to answers this )

The results that i want would look like this eventId = 1, EventName = Gig1. ArtistLineup = Led Zep, The beatles

So i need to create an alias ArtistLineup that would list all the artist. Via an inner select i think.

Any thoughts on what this would look like.

From stackoverflow

• SQL Server doesn't have anything built in to concatenate values in one statement like that. You could build the strings, but it has to be done one at a time.

  However, you can get around this by building your own custom aggregate function (requires messy games with ActiveX objects in SQL Server 2000)

• you might want to try something like this: http://stackoverflow.com/questions/279444/why-does-this-sql-script-work-as-it-does

• Saw this in SQL Server Magazine- not great, and the total list will have an upper length limit, but:

  drop table event
  go
  
  drop table event_artist
  go
  
  create table event (eventid int, eventname varchar(255))
  go
  
  create table event_artist (eventid int, artistname varchar(255))
  go
  
  insert into event values (1, 'gig1')
  go
  
  insert into event values (2, 'gig2')
  go
  
  insert into event_artist values (1, 'Led Zip')
  go
  
  insert into event_artist values (1, 'The Beatles')
  go
  
  drop function Event_Display
  go
  
  create function Event_Display (@EventID int) returns varchar(2000) as
  begin
      declare @artistList varchar(2000)
      set @artistList=''
  
      select @artistList=@artistList + ', ' + isnull(artistname,'') 
      from event_artist 
      where eventid=@EventID
  
      return substring(@artistList,3,2000)  --eliminate initial comma
  end
  go
  
  select event.eventid, event.eventname, dbo.Event_Display(event.eventid) from event
  

                                                                                                                                                                                                                                                     
  1           gig1        Led Zip, The Beatles
  
  2           gig2     
  

• ScottK's answer is basically the one you want. Here's the rest of mine:

  The query: select e.*, dbo.ArtistList(e.EventId) as ArtistList from [event] e

  The function:
  CREATE FUNCTION ArtistList
  (
  -- Add the parameters for the function here
  @EventId int
  )
  RETURNS varchar(MAX)
  AS
  BEGIN
  -- Declare the return variable here DECLARE @ArtistList varchar(MAX)

  -- Add the T-SQL statements to compute the return value here
  SELECT @ArtistList = COALESCE(@ArtistList + ', ', '') + Artist
  FROM EventArtist
  WHERE EventId = @EventId
  
  -- Return the result of the function
  RETURN @ArtistList
  

  END
  GO
  

  The only difference between my answer and ScottK's you might take note of is my use of varchar(MAX). That should pretty much address any concerns about the list of artists being truncated.

  I've deleted my previous (incomplete) answer.

  Joel Coehoorn : That only works for one item at a time. He'd have to run those in a cursor if he wants more than one result, which is less than desirable.

  Scott A. Lawrence : Thanks for the comment. My revised answer addresses the issue you raised.

• You can use the clever FOR XML trick posted by Kevin Fairchild (I've modified it to take account of band names which will include spaces):

  /*
  create table [event] (eventid int, eventname varchar(255))
  create table event_artist (eventid int, artistname varchar(255))
  insert into [event] values (1, 'gig1')
  insert into [event] values (2, 'gig2')
  insert into event_artist values (1, 'Led Zip')
  insert into event_artist values (1, 'The Beatles')
  */
  
  SELECT  e.eventid
         ,e.eventname
         ,REPLACE(REPLACE(RTRIM((
                                 SELECT   artistname + '| '
                                 FROM     [event_artist]
                                 WHERE    eventid = e.eventid
                                FOR
                                 XML PATH('')
                                )), '| ', ', '), '|', '') AS artists
  FROM    [event] AS e
  

  Note that this requires columns in the FOR XML to be unnamed (named columns get an XML wrapper).