Query to normalize table/combine row text

I have a table (call it oldTable) with columns like so:

ID (int),Rank (int),TextLineNumber (int),SomeText (varchar)

The primarykey is multi-part: ID+Rank+TextLineNumber.

I'm trying to transform/join it into another table (call it newTable) with columns like so:

ID (int), Rank (int), CombinedText (varchar)

and the primary key would be ID+Rank.

ID and Rank on the new table are already populated, but I need a query that would update the CombinedText column of the newTable with the following considerations:

• The Rank given on the new table may not exist on the old table, in which case it needs to pick the highest available rank from the old table that is not greater than the rank on the new table.

• The CombinedText column is a string concatenation of the "SomeText" column from the old table, concatenated in order of "TextLineNumber" using the Rank found from the first consideration.

Here's some example data:

old-
http://i54.tinypic.com/jq0vmx.png

new-
http://i53.tinypic.com/dhfyn8.png

I'm using MSSql 2005 if that matters.
I currently do this using T-SQL and while loops, but it's become a serious performance bottle neck (taking about 1 minute for 10000 rows).

Edit: Expanded example data in CSV:

Old:

ID,Rank,LineNumber,SomeText
1,1,1,the qu  
1,1,2,ick br  
1,1,3,own  
1,2,1,some te  
1,2,2,xt  
1,3,1,sample  
2,7,1,jumped ov  
2,7,2,er the  
2,7,3,lazy  
2,13,1,samp  
2,13,2,le text  
3,1,1,ABC  
3,1,2,DEF  
3,1,3,GHI  
3,1,4,JKL  
3,50,1,XYZ

New:

ID,Rank,CombinedText
1,2,some text
2,13,sample text
2,14,sample text
3,4,ABCDEFGHIJKL
3,5,ABCDEFGHIJKL
3,50,XYZ
3,55,XYZ

edit2:

Here's an example query that I found that does work but isn't fast enough (relying on multiple sub-queries):

```
update newtable set combinedtext =
coalesce ((select top 1 sometext from OldTable where OldTable.id=newtable.id and oldtable.rank=(select top 1 rank from oldtable where oldtable.id=newtable.id and oldtable.rank<=newtable.rank order by rank desc) and

This should work, I will clean it up later so its more efficient.

DECLARE @Old TABLE ( 
  id         INT, 
  rank       INT, 
  linenumber INT, 
  sometext   VARCHAR(1000)) 
DECLARE @New TABLE ( 
  id           INT, 
  rank         INT, 
  combinedtext VARCHAR(1000)) 

;WITH combinedresults(ctid, id, rank, linenumber, combinedtext) 
     AS (SELECT 0, 
                id, 
                rank, 
                linenumber, 
                CAST (sometext AS VARCHAR(8000)) 
         FROM   @Old o 
         WHERE  NOT EXISTS (SELECT TOP 1 1 
                            FROM   @Old 
                            WHERE  id = o.id 
                                   AND rank = o.rank 
                                   AND linenumber  ct.linenumber) 

UPDATE n 
SET    combinedtext = ct.combinedtext 
FROM   @New n 
       INNER JOIN (SELECT n.id, 
                          n.rank, 
                          MAX(o.rank) orank 
                   FROM   @new n 
                          INNER JOIN @Old o 
                            ON n.id = o.id 
                               AND o.rank <= n.rank 
                   GROUP  BY n.id, 
                             n.rank) r 
         ON n.id = r.id 
            AND n.rank = r.rank 
       INNER JOIN (SELECT id, 
                          ct.rank, 
                          MAX(ctid) ctid 
                   FROM   combinedresults ct 
                   GROUP  BY ct.id, 
                             ct.rank) r2 
         ON r2.id = r.id 
            AND r2.rank = r.orank 
       INNER JOIN combinedresults ct 
         ON r.id = ct.id 
            AND ct.rank = r.orank 
            AND ct.ctid = r2.ctid 

SELECT * 
FROM   @New

StackExchange Database Administrators Q#2193, answer score: 2