title: Why Hive query doesn't support IN/EXIST operator?
body: <p>I take look at <a href="https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Joins" rel="nofollow">Hive Language Manual</a></p>
  
  <p>and recognize Hive query doensn't support IN/EXIST operator and they suggest using LEFT SEMI JOIN as a replacement. Do you know the reason why ?</p>