Question

Using SQL Server 2005 Full Text Search I’d like to return values within a % of the maximum relevance result for that search.

 SELECT 
 A.ActivityID,
 KEY_TBL.Rank as Relevance, 
 DENSE_RANK() OVER (ORDER BY  Rank DESC) as SearchRank
 FROM Activity A 
 INNER JOIN FREETEXTTABLE(vwActivitySearch, FTS,'My search expression') AS KEY_TBL ON A.ActivityID = KEY_TBL.[KEY]

returns:

    ActivityID  Relevance   SearchRank
    ----------- ----------- --------------------
    89378       242         1
    89406       242         1
    88083       236         2
    88214       236         2
    84007       197         3
    83434       197         3
    13017       172         4
    89247       164         5
    89346       164         5

Rather than return by rank, I’d like to return values that are greater than 90%, or some arbitrary percentage, of the maximum relevance, so in this example

 WHERE Relevance>(242*0.9). 

I’m sure there’s a simple way to achieve this, but I can’t see it.

Some constraints –

• The query is a CTE expression within a UDF.
• I could easily run an initial query to obtain @MAXRelevance= SELECT MAX(Relevance)… then use Max(Relevance) in a WHERE clause, but full text search does not guarantee to return the same absolute values for relevance results on repeated searches.

Existing function:

 CREATE FUNCTION [dbo].[xxActivitySearch] (@SearchTerm varchar(255)='',@ResultDepth int)
 RETURNS @ReturnTable Table (ActivityID int,Relevance int,SearchRank int)
 AS
 BEGIN
 WITH T AS (
 SELECT 
   A.ActivityID,
   KEY_TBL.Rank as Relevance, 
   DENSE_RANK() OVER (ORDER BY  Rank DESC) as SearchRank
 FROM Activity A 
INNER JOIN FREETEXTTABLE(vwActivitySearch, FTS,@SearchTerm) AS KEY_TBL ON A.ActivityID=KEY_TBL.[KEY])
INSERT @ReturnTable SELECT * FROM T WHERE (SearchRank<=@ResultDepth)
RETURN
END 

Answer 1

WITH T AS
(
SELECT A.ActivityID,
       KEY_TBL.Rank                           as Relevance,
       DENSE_RANK() OVER (ORDER BY Rank DESC) as SearchRank,
       MAX(KEY_TBL.Rank) OVER() AS MaxRelevance
FROM   Activity A
       INNER JOIN 
         FREETEXTTABLE(vwActivitySearch, FTS, 'My search expression') AS KEY_TBL
         ON A.ActivityID = KEY_TBL.[KEY]  

)
SELECT ActivityID,
       Relevance,
       SearchRank
FROM T
WHERE Relevance>(MaxRelevance*0.9)