Alter a table column

Use the ALTER TABLE command to add new columns, drop non-primary key columns, or rename a primary key column.

To change the table settings, see Altering table properties.

Prerequisites

Add a column

Add an age column of type int to the table cycling.cyclist_alt_stats.

ALTER TABLE cycling.cyclist_alt_stats 
ADD cyclist_age int;

The ALTER TABLE command creates the column metadata, adds the column to the table schema, and sets the value to null for all rows.

Verify that a column is added

Verify that the column was added with null values.

CQL
Result

SELECT id, cyclist_age AS age
FROM cycling.cyclist_alt_stats
LIMIT 3;

 id                                   | age
--------------------------------------+------
 e0953617-07eb-4c82-8f91-3b2757981625 | null
 a9e96714-2dd0-41f9-8bd0-557196a44ecf | null
 ed584e99-80f7-4b13-9a90-9dc5571e6821 | null

(3 rows)

The result set shows the first three rows.

Rename a column

Rename the `id` primary key column to `cyclist_id`.

ALTER TABLE cycling.cyclist_alt_stats 
RENAME id TO cyclist_id;

Restriction: Only primary key columns can be renamed.

Add a collection column

Alter the table cycling.upcoming_calendar to add a map named description to store a name and description for each race.

ALTER TABLE cycling.upcoming_calendar 
ADD description map<text,text>;

Verify the collection column

Verify the results:

CQL
Result

SELECT description
FROM cycling.upcoming_calendar
WHERE year = 2015
  AND month = 6;

Map type columns display in a JSON format.

 description
------------------------------------------------------------------------------
 {'Criterium du Dauphine': 'Easy race', 'Tour du Suisse': 'Hard uphill race'}

(1 rows)

Related information:

ALTER TABLE