PL/SQL User's Guide and Reference

Retrieving Query Results into Collections with the BULK COLLECT Clause
In the next example, the SQL engine loads all the values in an object column into a
nested table before returning the table to the PL/SQL engine:
CREATE TYPE Coords AS OBJECT (x NUMBER, y NUMBER);
CREATE TABLE grid (num NUMBER, loc Coords);
INSERT INTO grid VALUES(10, Coords(1,2));
INSERT INTO grid VALUES(20, Coords(3,4));
DECLARE
TYPE CoordsTab IS TABLE OF Coords;
pairs CoordsTab;
BEGIN
SELECT loc BULK COLLECT INTO pairs FROM grid;
-- now pairs contains (1,2) and (3,4)
END;
The SQL engine initializes and extends collections for you. (However, it cannot
extend varrays beyond their maximum size.) Then, starting at index 1, it inserts
elements consecutively and overwrites any pre-existent elements.
The SQL engine bulk-binds entire database columns. So, if a table has 50,000 rows,
the engine loads 50,000 column values into the target collection. However, you can
use the pseudocolumn ROWNUM to limit the number of rows processed. In the
following example, you limit the number of rows to 100:
DECLARE
TYPE SalList IS TABLE OF emp.sal%TYPE;
sals SalList;
BEGIN
SELECT sal BULK COLLECT INTO sals FROM emp
WHERE ROWNUM 1000;
names NameList;
PL/SQL Collections and Records 5-47