I was trying out hive alter by adding new columns to existing table. 
 
I have set up a hive external table on top of HDFS ( CSV serde).. and later added a column .    when run a query , im getting nulls on a new column.. this is as expected.  however, i have ingested data(includes newly added column) now into HDFS  and when i run query again.. im still getting nulls on new column.  
 
can you pls help me why this is occurring ? do i need to run any commands ( analyze stats etc to get a values for newly added column)?
 
Also, when i drop and recreate external table ..its working as expected .    
 
appreciate your help.