Expanding Your Data Model - Learning Apache Cassandra - page 144

Recall from Chapter 2 , The First Table that Cassandra does not have the concept of NULL
values in the sense that SQL databases do; rather, the null displayed by cqlsh simply
indicates that the rows do not have data in the location column.
Note
For a full account of the ALTER TABLE command, refer to the DataStax CQL docu-
mentation at http://www.datastax.com/documentation/cql/3.1/cql/cql_reference/al-
ter_table_r.html