是否有MULTISET运算符的替代方法可以避免子查询？

Question

假设您有一个表格如下:

CREATE TABLE EMPLOYEE_SALES
(
    EMPLOYEE_ID NUMBER,
    PRODUCT_ID  NUMBER,
    SALE_AMOUNT NUMBER
);

并假设它填充如下:

+-------------+------------+-------------+
| EMPLOYEE_ID | PRODUCT_ID | SALE_AMOUNT |
+-------------+------------+-------------+
|      1      |     100    |       1.05  |
|      1      |     200    |      45.67  |
|      2      |     100    |       3.25  |
|      2      |     200    |      34.29  |
+-------------+------------+-------------+

现在,假设我创建了一个SALE_TYPE代表(PRODUCT_ID, SALE_AMOUNT)元组的自定义类型:

CREATE TYPE SALE_TYPE IS OBJECT
(
  PRODUCT_ID  NUMBER,
  SALE_AMOUNT NUMBER
);

并假设我还创建了一个名为的自定义类型SALES_TYPE,表示以下TABLE内容SALE_TYPE:

CREATE TYPE SALES_TYPE IS TABLE OF SALE_TYPE;

我想通过查询EMPLOYEE_SALES表组EMPLOYEE_ID.对于每一个EMPLOYEE_ID,我希望创建一个SALES_TYPE包含该员工的销售额.根据文档,我会做这样的事情:

SELECT
  EMPLOYEE_ID,
  CAST
  (
    MULTISET
    (
      SELECT
        PRODUCT_ID,
        SALE_AMOUNT
      FROM
        EMPLOYEE_SALES inner_employee_sales
      WHERE
        inner_employee_sales.employee_id = employee_sales.employee_id
    ) AS SALES_TYPE
  ) AS SALES
FROM
  EMPLOYEE_SALES
GROUP BY
  EMPLOYEE_ID

我希望这个查询产生这样的东西:

+-------------+------------------------------+
| EMPLOYEE_ID | SALES                        |
+-------------+------------------------------+
|     1       | +------------+-------------+ |
|             | | PRODUCT_ID | SALE_AMOUNT | |
|             | +------------+-------------+ |
|             | |    100     |        1.05 | |
|             | |    200     |       45.67 | |
|             | +------------+-------------+ |
+-------------+------------------------------+
|     2       | +------------+-------------+ |
|             | | PRODUCT_ID | SALE_AMOUNT | |
|             | +------------+-------------+ |
|             | |    100     |        3.25 | |
|             | |    200     |       34.29 | |
|             | +------------+-------------+ |
+-------------+------------------------------+

有没有办法在不发出子查询的情况下获得相同的结果(我正在处理的真实查询比这个人为的例子复杂得多)？例如,有这样的事情:

SELECT
  EMPLOYEE_ID,
  CAST
  (
    COLLECT_ALL_RECORDS_WITHIN_THE_CURRENT_GROUP(
      PRODUCT_ID,
      SALE_AMOUNT
    )
    AS SALES_TYPE
  ) AS SALES
FROM
  EMPLOYEE_SALES
GROUP BY
  EMPLOYEE_ID

Answer 1

在Oracle 10g中,您可以使用COLLECT运算符,如下所示:

select employee_id, 
       cast(collect(sale_type(product_id, sale_amount)) as sales_type)
from employee_sales
group by employee_id