¿Cómo combino datos de varias filas en una sola?

Usando PIVOT puede hacer lo siguiente

With SampleData AS 
(
SELECT 'Team1' as Team , 'example@sqldat.com' as email, 'A' as Groups
UNION SELECT 'Team1' as Team , 'example@sqldat.com' as email, 'B' as Groups
UNION SELECT 'Team1' as Team , 'example@sqldat.com' as email, 'C' as Groups
UNION SELECT 'Team2' as Team , 'example@sqldat.com' as email, 'A' as Groups
UNION SELECT 'Team2' as Team , 'example@sqldat.com' as email, 'B' as Groups
UNION SELECT 'Team2' as Team , 'example@sqldat.com' as email, 'C' as Groups
)
SELECT Team, A, B,C FROM 
(SELECT * FROM SampleData) source
PIVOT
(MAX(email) FOR Groups IN ([A], [B], [C]) )as pvt

Produce

Team  A                B                C
----- ---------------- ---------------- ----------------
Team1 example@sqldat.com example@sqldat.com example@sqldat.com
Team2 example@sqldat.com example@sqldat.com example@sqldat.com

Vea un ejemplo de Data.SE en funcionamiento

En una base de datos que no es compatible con PIVOT, puede realizar múltiples combinaciones en su tabla. Aunque es posible que desee hacerlo de todos modos, ya que, como señaló GBN, ya que no estamos utilizando un agregado.

With SampleData AS 
(
SELECT 'Team1' as Team , 'example@sqldat.com' as email, 'A' as Groups
UNION SELECT 'Team1' as Team , 'example@sqldat.com' as email, 'B' as Groups
UNION SELECT 'Team1' as Team , 'example@sqldat.com' as email, 'C' as Groups
UNION SELECT 'Team2' as Team , 'example@sqldat.com' as email, 'A' as Groups
UNION SELECT 'Team2' as Team , 'example@sqldat.com' as email, 'B' as Groups
UNION SELECT 'Team2' as Team , 'example@sqldat.com' as email, 'C' as Groups
)

SELECT 
    source.Team,
    A.email,
    B.email,
    C.email
FROM 
    (SELECT DISTINCT TEAM From SampleData) source
    LEFT JOIN SampleData A 
    ON source.Team = A.Team
     AND A.GROUPS = 'A'
    LEFT JOIN SampleData B 
    ON source.Team = B.Team
    AND B.GROUPS = 'B'
    LEFT JOIN SampleData C 
    ON source.Team = C.Team
    AND C.GROUPS = 'C'

Vea un ejemplo de Data.SE