在PostgreSQL中循环时如何选择多个列？

Question

Please tell me how to do this i want to select multiple column while looping..

create or replace function insert_date_dimension("date" date)
 returns setof date as $$
declare
    dat date;
    start_date date;
    end_date date;
begin
    start_date := '2016/01/01';
    end_date := '2016/12/31';
    while start_date <= end_date loop
        --return next  start_date;
        select start_date,date_part('week',start_date),date_part('quarter',start_date),to_char(start_date, 'day'),to_char(start_date, 'month'),
        extract(year from current_date),extract(month from current_date);
        start_date:= start_date + interval  '1 day';
    end loop;
end;

$$ language plpgsql;

ERROR:  query "SELECT    start_date,date_part('week',start_date),date_part('quarter',start_date),to_char(start_date, 'day'),to_char(start_date, 'month'),
        extract(year from current_date),extract(month from current_date)" returned 7 columns

CONTEXT: PL/pgSQL function insert_date_dimension(date) line 11 at RETURN NEXT

Answer 1

The error occurs because you would have to use SELECT ... INTO ... in a PL/pgSQL function. Besides, you forgot to RETURN something.

It is much easier to use generate_series ; that way you probably don't even need to define a function, you could just use INSERT INTO ... SELECT ... .

Here is the function as I would write it:

CREATE OR REPLACE FUNCTION insert_date_dimension(
   OUT "date" date,
   OUT week integer,
   OUT quarter integer,
   OUT dayname text,
   OUT monthname text,
   OUT year integer,
   OUT month integer
) RETURNS SETOF RECORD STABLE LANGUAGE plpgsql AS
$$DECLARE
   dat date;
   start_date timestamp := '2016-01-01 00:00:00';
   end_date timestamp := '2016-12-31 00:00:00';
BEGIN
   RETURN QUERY SELECT
         d::date,
         date_part('week', d)::integer,
         date_part('quarter', d)::integer,
         to_char(d, 'day'),
         to_char(d, 'month'),
         date_part('year', d)::integer,
         date_part('month', d)::integer
      FROM generate_series(start_date, end_date, '1 day') d(d);
END;$$;