How to Add a Column in Redshift

The new column is appended at the end, since Redshift has no AFTER or FIRST. Adding a column with a default does not rewrite the table. You cannot add a NOT NULL column unless the table is empty, and the column encoding is chosen automatically unless you specify ENCODE.

ALTER TABLE orders ADD COLUMN discount NUMERIC(5,2) DEFAULT 0;

Multiple columns need multiple statements

Redshift permits exactly one ADD COLUMN per ALTER TABLE, which trips up migrations copied over from Postgres. Each statement is fast on its own, so the limitation costs clarity rather than time. You also cannot make the new column a DISTKEY or SORTKEY after the fact; that requires recreating the table.

ALTER TABLE orders ADD COLUMN status VARCHAR(32);
ALTER TABLE orders ADD COLUMN updated_at TIMESTAMP;