Adding to Alan's points external tables are used often as a staging area.
For example, ingesting data from HDFS location on a daily basis and putting
that data into Hive managed tables. That location of that external table
can change pointing to a new HDFS directory created by say Flume etc
through
Hive does not assume that it owns the data for an external table. Thus when an
external table is dropped, the data is not deleted. People often use this as a
way to load data into a directory in HDFS and then “cast” a table structure
over it by creating an external table with that directory as
