Como combino dados de várias linhas em uma?

Usando PIVOT Você pode fazer o seguinte

With SampleData AS 
(
SELECT 'Team1' as Team , '[email protected]' as email, 'A' as Groups
UNION SELECT 'Team1' as Team , '[email protected]' as email, 'B' as Groups
UNION SELECT 'Team1' as Team , '[email protected]' as email, 'C' as Groups
UNION SELECT 'Team2' as Team , '[email protected]' as email, 'A' as Groups
UNION SELECT 'Team2' as Team , '[email protected]' as email, 'B' as Groups
UNION SELECT 'Team2' as Team , '[email protected]' 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

Produz

Team  A                B                C
----- ---------------- ---------------- ----------------
Team1 [email protected] [email protected] [email protected]
Team2 [email protected] [email protected] [email protected]

Veja um exemplo do Data.SE em funcionamento

Em um banco de dados que não suporta PIVOT, você pode fazer várias junções à sua tabela. Embora você possa querer de qualquer maneira, como GBN apontou, já que não estamos usando um agregado.

With SampleData AS 
(
SELECT 'Team1' as Team , '[email protected]' as email, 'A' as Groups
UNION SELECT 'Team1' as Team , '[email protected]' as email, 'B' as Groups
UNION SELECT 'Team1' as Team , '[email protected]' as email, 'C' as Groups
UNION SELECT 'Team2' as Team , '[email protected]' as email, 'A' as Groups
UNION SELECT 'Team2' as Team , '[email protected]' as email, 'B' as Groups
UNION SELECT 'Team2' as Team , '[email protected]' 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'

Veja um exemplo do Data.SE em funcionamento