The WHILE statement keeps executing a block of statements while a particular condition is met. Its syntax is as follows:

[ <<label>> ]
WHILE boolean-expression LOOP
    statements
END LOOP [ label ];

The following example uses the while loop to print the days of the current month:

DO $$
DECLARE
  first_day_in_month date := date_trunc('month', current_date)::date;
  last_day_in_month date := (date_trunc('month', current_date)+ INTERVAL '1 MONTH - 1 day')::date;
  counter date = first_day_in_month;
BEGIN
  WHILE (counter <= last_day_in_month) LOOP
    RAISE notice '%', counter;
    counter := counter + interval '1 day';
  END LOOP;
END;
$$ LANGUAGE plpgsql;