Altering a table to add a collection

Add collection columns to a table or change existing collection columns with the ALTER TABLE command.

Use the ALTER TABLE command to add a collection column to a table.

Procedure

Alter the table cycling.upcoming_calendar to add a collection map description to store a description for each race listed.
```
ALTER TABLE cycling.upcoming_calendar ADD description map<text,text>;
```

After updating cycling.upcoming_calendar table to insert some data, description can be displayed.

UPDATE cycling.upcoming_calendar 
SET description = description + {'Criterium du Dauphine' : 'Easy race', 'Tour du Suisse' : 'Hard uphill race'} 
WHERE year = 2015 AND month = 6;

Verify the results.

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)