SELECT
SubscriberKey, EmailAddress, Consent_Level_Summary__c, Region, LanguageCode

FROM (
SELECT
DISTINCT LOWER(Email__c) AS EmailAddress, c.Id AS SubscriberKey, c.Consent_Level_Summary__c, 
CASE WHEN i.Region__c IS NOT NULL THEN i.Region__c ELSE lkup.Region END AS Region,
CASE WHEN c.Language__c IS NOT NULL THEN c.Language__c END AS LanguageCode, 

ROW_NUMBER() OVER(PARTITION BY c.ID ORDER BY i.LastModifiedDate DESC) as RowNum

FROM ep_mr_en_us_w170049_MASTER mstr 
JOIN ent.Interaction__c_Salesforce i ON LOWER(mstr.EmailAddress) = LOWER(i.Email__c)
JOIN ent.Contact_Salesforce_1 c ON LOWER(c.Email) = LOWER(i.Email__c)
INNER JOIN ENT.CountryCode_Language_Lookup lkup ON mstr.Mailing_Country__c = lkup.CountryCode

WHERE
    mstr.EmailAddress IS NOT NULL
)t2

WHERE RowNum = 1