Если кому-то интересно здесь было мое решение, основанное на ответ Энди:
ВЫБРАТЬ
Week,
IF (SocialNetwork IS NULL, Medium, "social") AS Medium,
Referral_URL,
SocialNetwork,
Total_Sessions,
Avg_Time_On_Site_in_Mins,
Avg_Session_Page_Depth,
Bounce_Rate,
ОТ (
SELECT
Week,
Medium,
Referral_HostName,
Referral_URL,
SocialNetworks.socialNetwork AS SocialNetwork,
Total_Sessions,
Avg_Time_On_Site_in_Mins,
Avg_Session_Page_Depth,
Bounce_Rate,
FROM
[zzzzzzz.ga_sessions_20141223] AS All_Sessions
LEFT JOIN EACH [GA_API.SocialNetworks] AS SocialNetworks
ON ALL_Sessions.Referral_HostName = SocialNetworks.Source
GROUP EACH BY Week, Medium, Full_URL, Referral_HostName, Referral_URL, SocialNetwork, Total_Sessions, Avg_Time_On_Site_in_Mins, Avg_Session_Page_Depth, Bounce_Rate,
ORDER BY Total_Sessions DESC)
GROUP КАЖДЫЙ неделям Medium, Full_URL, Referral_URL, SocialNetwork, Total_Sessions, Avg_Time_On_Site_in_Mins, Avg_Session_Page_Depth, Bounce_Rate, ORDER BY Total_Sessions DESC;