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 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 the column was added with null values.

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

Results

The result set shows the first three rows.

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.

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 results:

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

Results

Map type columns display in a JSON format.