Modify table columns

Add, drop, or rename table columns.

• 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;

  The result set shows the first three rows.

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

• Drop the cyclist_age column from the table.

  ALTER TABLE cycling.cyclist_alt_stats 
  DROP cyclist_age int;

• 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.