How to alter a column’s data type in a PostgreSQL table?

Entering the following command into a PostgreSQL interactive terminal results in an error:

ALTER TABLE tbl_name ALTER COLUMN col_name varchar (11);

What is the correct command to alter the data type of a column?

Answer

See documentation here: http://www.postgresql.org/docs/current/interactive/sql-altertable.html

ALTER TABLE tbl_name ALTER COLUMN col_name TYPE varchar (11);