1) The SQL syntax that Hive supports is quite restrictive. So for example, we are not

allowed to do sub-queries, which is very very common in the SQL world. There is no windowed aggregates, and also ANSI joins are not allowed. And in the SQL world there are a lot of other joins that the developers are used to which we cannot use with Hive.

2) The other restriction that is quite limiting is the data types that are supported, for example when it comes to Varchar support or Decimal support, Hive lacks quite severely

3) When it comes to client support the JDBC and the ODBC drivers are quite limited and there are concurrency problems when accessing Hive using these client drivers.