Group by sql query on comma joined column

Question

My table structure is like below, "Mail" column can contain multiple email joined by comma

Data(int)

Mail(v

Answer 1

A SQL Server Solution

WITH T ([Data], [Mail])
     AS (SELECT 1,'m1@gmail.com,m2@hotmail.com' UNION ALL
         SELECT 2,'m2@hotmail.com,m3@test.com')
SELECT address  AS Mail,
       COUNT(*) AS [Count]
FROM   T
       CROSS APPLY (SELECT CAST('' + REPLACE([Mail], ',', '') + ''
                                AS XML
                           ) AS x) ca1
       CROSS APPLY (SELECT T.split.value('.', 'varchar(200)') AS address
                    FROM   x.nodes('/m') T(split)) ca
GROUP  BY address