Deleting columns

Upon further consideration, we may decide that location is a better column name than city_state. Cassandra does not allow us to rename existing data columns; however, since we haven't put any data in the city_state column yet, we can achieve our goals simply by dropping the city_state column and adding a location column instead:

ALTER TABLE "users" DROP "city_state";
ALTER TABLE "users" ADD "location" text;

The DROP command within the ALTER TABLE statement looks just like the ADD command, except that we need not specify the column's type; only its name is sufficient. Looking at the output of DESCRIBE again, we've now got the columns set up the way we'd like:

Now that we've got our expanded schema, we can take a look at the actual contents of the table:

SELECT * FROM "users";

The output now includes our new location column:

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...