Oracle BULK COLLECT INTO批量操作应用

在Oracle开发中，有时我们会使用BULK COLLECT INTO批量操作大量的数据，如果没有LIMIT限制，则Oracle会读取查询的所有记录行到内存中，这样很容易造成PGA溢出而导致出现错误。所以使用LIMIT关键字可以避免PGA溢出。

示例：

SQL> DECLARE
  2    TYPE typ_emp IS TABLE OF emp%ROWTYPE INDEX BY PLS_INTEGER;
  3    v_emp typ_emp;
  4
  5    v_emp_id   tab_emp_id;
  6    v_total_id tab_emp_id := tab_emp_id();
  7
  8    v_limit NUMBER := 3;
  9
 10    v_test emp%ROWTYPE;
 11
 12    CURSOR cur_emp IS
 13      SELECT * FROM emp;
 14  BEGIN
 15    OPEN cur_emp;
 16
 17    LOOP
 18      FETCH cur_emp BULK COLLECT
 19        INTO v_emp LIMIT v_limit;
 20
 21      FORALL j IN v_emp.first .. v_emp.last
 22        INSERT INTO t_emp
 23        VALUES
 24          (seq_emp.nextval,
 25           v_emp(j).ename)
 26        RETURNING id BULK COLLECT INTO v_emp_id;
 27
 28      v_total_id := v_total_id MULTISET UNION ALL v_emp_id;
 29      EXIT WHEN v_emp.count < v_limit;
 30
 31    END LOOP;
 32
 33    CLOSE cur_emp;
 34
 35    FOR rec IN (SELECT *
 36                  FROM t_emp
 37                 WHERE id IN (SELECT column_value FROM TABLE(v_total_id)))
 38    LOOP
 39      dbms_output.put_line(rec.id || '---------->' || rec.name);
 40    END LOOP;
 41
 42    COMMIT;
 43
 44  END;
 45  /
86---------->SMITH_甯
87---------->ALLEN
88---------->WARD
89---------->JONES
90---------->MARTIN
91---------->BLAKE
92---------->CLARK
93---------->SCOTT
94---------->KING
95---------->TURNER
96---------->ADAMS
97---------->JAMES
98---------->FORD
99---------->MILLER

PL/SQL procedure successfully completed.

SQL>