Tables

The concept of a table in Hive is very similar to the table in the relational database. Each table maps to a directory, which is under /user/hive/warehouse by default in HDFS. For example, /user/hive/warehouse/employee is created for the employee table. All the data in the table is stored in this hive user-manageable directory (full permission). This kind of table is called an internal, or managed, table. When data is already stored in HDFS, an external table can be created to describe the data. It is called external because the data in the external table is specified in the LOCATION property rather than the default warehouse directory. When keeping data in the internal tables, the table fully manages the data in it. When an internal table is dropped, its data is deleted together. However, when an external table is dropped, the data is not deleted. It is quite common to...