Check this out!

DECLARE @tblFQDNInfo TABLE( Value VARCHAR(8), Data VARCHAR(128))

INSERT INTO @tblFQDNInfo

EXEC [master]..xp_instance_regread N'HKEY_LOCAL_MACHINE', N'SYSTEM\ControlSet001\Services\Tcpip\Parameters', N'Hostname'

INSERT INTO @tblFQDNInfo

EXEC [master]..xp_instance_regread N'HKEY_LOCAL_MACHINE', N'SYSTEM\ControlSet001\Services\Tcpip\Parameters', N'Domain'

SELECT tfi1.Data + N'.' + tfi2.Data FQDN

FROM @tblFQDNInfo tfi1, ...

DECLARE @String VARCHAR(32) = N'shfdiuf/lsdfsjfij'

SELECTLEFT(@String, CHARINDEX(N'/', @String) - 1),

RIGHT(@String, CHARINDEX(N'/', @String) + 1)