假设您有一个表(在 Oracle 中):
CREATE TABLE CUSTOMER
(
customer_id NUMBER,
gender CHAR(1)
);
假设您有一个表类型:
CREATE TYPE NUMBER_TABLE_TYPE AS TABLE OF NUMBER;
是否可以编写一个 GROUP BY
查询,以便对于每个组,该组的主键字段都存储在 NUMBER_TABLE_TYPE
中?例如:
DECLARE
CURSOR gender_cursor IS
SELECT
gender,
/* The CUSTOMER_IDS column will be of type NUMBER_TABLE_TYPE: */
SOME_MAGICAL_AGGREGATE_FUNCTION(customer_id) AS customer_ids
FROM
CUSTOMER
GROUP BY
gender;
customer_ids NUMBER_TABLE_TYPE;
BEGIN
FOR gender IN gender_cursor LOOP
customer_ids := gender.customer_ids;
FOR i IN customer_ids.FIRST .. customer_ids.LAST LOOP
dbms_output.put_line(customer_ids(i));
END LOOP;
END LOOP;
END;
我知道这应该通过使用两个游标来完成(一个用于性别组,另一个用于查询每个组的客户)。我只是好奇这是否可以做到。 :)
最佳答案
有两种方法可以实现这一点。 首先,通过分析来获取每行上该性别的所有记录的计数。
DECLARE
CURSOR gender_cursor IS
SELECT gender, customer_id, count(*) over (partition by gender) cnt_in_gender,
FROM CUSTOMER
ORDER BY gender;
v_prev_gender varchar2(1) := '?';
BEGIN
FOR gender IN gender_cursor LOOP
IF gender.gender != v_prev gender then
dbms_output.put_line('You will now see '||gender.cnt_in_gender);
v_prev_gender := gender.gender);
END IF;
dbms_output.put_line(gender.customer_ids);
END LOOP;
END;
其次,更接近您的要求
DECLARE
CURSOR gender_cursor IS
SELECT
gender,
/* The CUSTOMER_IDS column will be of type NUMBER_TABLE_TYPE: */
CAST(COLLECT(customer_id) AS NUMBER_TABLE_TYPE) AS customer_ids
FROM
CUSTOMER
GROUP BY
gender;
customer_ids NUMBER_TABLE_TYPE;
BEGIN
FOR gender IN gender_cursor LOOP
customer_ids := gender.customer_ids;
FOR i IN customer_ids.FIRST .. customer_ids.LAST LOOP
dbms_output.put_line(customer_ids(i));
END LOOP;
END LOOP;
END;
关于oracle - 在 GROUP BY 查询中将值聚合到表类型中,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3367579/