In Oracle:

SET SERVEROUTPUT ON;

DECLARE result VARCHAR2(32767) := ''; num INTEGER := 0;

-- Cursor to generate numbers from 1 to 1000
CURSOR c1 IS (SELECT LEVEL n FROM dual CONNECT BY LEVEL <= 1000);

-- Function to check if a number is prime
FUNCTION is_prime(n INTEGER) RETURN BOOLEAN IS
    divisor INTEGER;
BEGIN
    IF n < 2 THEN
        RETURN FALSE;
    ELSIF n IN (2, 3, 5) THEN
        RETURN TRUE;
    ELSIF MOD(n, 2) = 0 OR MOD(n, 3) = 0 OR MOD(n, 5) = 0 THEN
        RETURN FALSE;
    END IF;

    divisor := 7;
    WHILE divisor * divisor <= n LOOP
        IF MOD(n, divisor) = 0 THEN
            RETURN FALSE;
        END IF;
        divisor := divisor + 2;  -- Skip even numbers
    END LOOP;

    RETURN TRUE;
END is_prime;

BEGIN FOR c1_rec IN c1 LOOP IF is_prime(c1_rec.n) THEN result := result || c1_rec.n || '&'; END IF; END LOOP;

-- Trim the last '&' and output result
dbms_output.PUT_LINE(TRIM(TRAILING '&' FROM result));

END; /