Q&A for professional mathematicians
; with texts_cte as ( SELECT DISTINCT c.Text AS Text FROM Comments c JOIN Posts p ON (c.PostId=p.Id) AND (p.OwnerUserId=##UserId##) WHERE (c.Text LIKE '%@%') ) , substrings_cte AS ( SELECT substring(Text,charindex('@',Text), len(Text)) AS TextFrom FROM texts_cte ), names AS ( SELECT substring(TextFrom,1,patindex('%[ :,.]%',TextFrom+' ')-1) AS Reply FROM substrings_cte ) SELECT Reply, Count(*) AS Count FROM Names GROUP BY Reply ORDER BY Count(*) DESC