June 10 (Reuters) - Salesforce.com Inc said on Monday it would buy data analytics platform Tableau Software in an all-stock deal valued at $15.7 billion. Tableau shareholders will get 1.103 Salesforce shares, valuing the offer at $177.88 per share, which represents a premium of 42% to Tableau's Friday closing price. (Reporting by Arjun Panchadar in Bengaluru; Editing by Arun Koyyur)