How to print multiple row values in postgres when query executed using EXECUTE?

Question

I have below program , My 2nd select query returns multiple records, How should I print all the values.. Currently its printing only 1st value. Can you please suggest?

Ex. Actual Output:

123

890

4599

Current Output: 123

DO $$
<<script>>
DECLARE
  student_rec RECORD;
  sqlquery text;
  v_nk RECORD;

BEGIN
FOR student_rec IN 
select nk from course_table;
-- open loop for cursor above
LOOP
sqlquery := 'SELECT col FROM section where rec_nk = ' || '''' ||student_rec.nk ||'''' ;
EXECUTE sqlquery into v_nk; 
raise notice 'Value: %', v_nk;  
END LOOP; 

EXCEPTION when others then    
    raise notice 'Script execution failed.'
                 'Transaction was rolled back.';
    raise notice '% %', SQLERRM, SQLSTATE;

END script $$;

Answer 1

Even if you have declared v_nk as RECORD, SELECT INTO indeed selects a value into a scalar value, when used in the context of PL/pgSQL. See SELECT INTO documentation for more details.

If you want to print all records with RAISE NOTICE you can loop like this:

sqlquery := 'SELECT col FROM section WHERE rec_nk = ' || '''' || student_rec.nk || '''' ;

FOR v_nk IN EXECUTE sqlquery
    LOOP
        RAISE NOTICE 'Value: %', v_nk;
    END LOOP;

Answer 2

You already are looping through query result:

[ <<label>> ]
FOR target IN query LOOP
    statements
END LOOP [ label ];

There is also FOR-IN-EXECUTE:

[ <<label>> ]
FOR target IN EXECUTE text_expression [ USING expression [, ... ] ] LOOP
    statements
END LOOP [ label ];

See documentation on Looping Through Query Results.

In your case it would be:

FOR v_nk IN EXECUTE sqlquery LOOP
    RAISE NOTICE 'Value: %', v_nk;
END LOOP;