От тук:http://web.archive.org/web/20080701045806/http://sqlserver2000.databases.aspfaq.com:80/how-do-i-get-a-list-of-sql-server-tables -and-their-row-counts.html
SELECT
[TableName] = so.name,
[RowCount] = MAX(si.rows)
FROM
sysobjects so,
sysindexes si
WHERE
so.xtype = 'U'
AND
si.id = OBJECT_ID(so.name)
GROUP BY
so.name
ORDER BY
2 DESC