Removing an optional column safely with PostgreSQL 9+

Simply include IF EXIST in the statement you're using for DROP COLUMN:

ALTER TABLE targetTable DROP COLUMN
IF EXISTS targetColumn;

Another option is the IF EXISTS approach, which works nicely when we're performing a migration

DO $$
BEGIN
  IF EXISTS (
    SELECT column_name
    FROM information_schema.columns
    WHERE table_name = targetTable AND column_name = targetColumn
  ) THEN
    ALTER TABLE targetTable DROP COLUMN targetColumn;
  END IF;
END $$;