Update column definitions in Redshift

update-col-in-Redshift.sql

-- create a new temp table with exact same schema
CREATE TABLE foobar_temp (LIKE foobar INCLUDING DEFAULTS);

-- or create this temp table with any new schema (eg updated col type)
CREATE TABLE foobar_temp (...)

-- copy everything from old table
INSERT INTO foobar_temp <list of columns> SELECT <list of columns> FROM foobar;

-- rename/drop tables
ALTER TABLE foobar RENAME TO foobar_old;
ALTER TABLE foobar_temp RENAME TO foobar;
DROP TABLE foobar_old;