join tables

Do you always have 1 row per doc in table2 or can there be more rows?
Basically you can COUNT the rows per doc in table2 and divide the word_count by that number.

Hm, still not entirely sure if I understand you, but is it this what you are looking for?
DECLARE @table1 TABLE (DOC int, WORD_COUNT int);

INSERT INTO @table1
(DOC, WORD_COUNT)
VALUES
(1848023, 221);

INSERT INTO @table1
(DOC, WORD_COUNT)
VALUES
(1848024, 300);

DECLARE @table2 TABLE (DOC int, CREATION_DATE datetime);

INSERT INTO @table2
(DOC, CREATION_DATE)
VALUES
(1848023 ,'2010-03-07 18:23:00.000');

INSERT INTO @table2
(DOC, CREATION_DATE)
VALUES
(1848024 ,'2010-01-07 18:23:00.000');

SELECT
T1.DOC,
T1.WORD_COUNT,
T2.CREATION_DATE,
1 + DATEDIFF(MONTH, T2.CREATION_DATE, GETDATE()) AS NumberOfmonths,
T1.WORD_COUNT * 1.0 / (1 + DATEDIFF(MONTH, T2.CREATION_DATE, GETDATE())) AS AvgWordCount
FROM
@table1 T1
JOIN
@table2 T2 ON T1.DOC = T2.DOC;
DOC WORD_COUNT CREATION_DATE NumberOfmonths AvgWordCount
1848023 221 2010-03-07 18:23:00.000 1 221.000000000000
1848024 300 2010-01-07 18:23:00.000 3 100.000000000000

(2 row(s) affected)

Frank, this is posted in 2008 forum
so
INSERT INTO @table2
(DOC, CREATION_DATE)
VALUES
(1848023 ,'2010-03-07 18:23:00.000');

INSERT INTO @table2
(DOC, CREATION_DATE)
VALUES
(1848024 ,'2010-01-07 18:23:00.000');
can be written
INSERT INTO @table2
(DOC, CREATION_DATE)
VALUES
(1848023 ,'2010-03-07 18:23:00.000'),
(1848024 ,'2010-01-07 18:23:00.000');

True, but we're still on 2005 here. []

<P mce_keep="true">[quote user="FrankKalis"] <P>True, but we're still on 2005 here. <IMG alt=Smile src="http://sql-server-performance.com/Community/emoticons/emotion-1.gif"> <BR></P><P>[/quote]</P><P>Ok. No problem []</P>