我有一个正在运行的查询，但我遇到了一些问题，我希望有人可以帮助我。
首先，我想做一个 JOIN 以在输出中包含客户的名字和姓氏。
其次，我想包含 customer_id 5，它没有数据，并且这些列应该为 NULL。
最后，我想包括自客户上次购买以来经过的天数。
以下是我的测试案例和尝试。任何帮助将不胜感激。
ALTER SESSION SET NLS_TIMESTAMP_FORMAT = 'DD-MON-YYYY HH24:MI:SS.FF';
ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';
CREATE TABLE customers
(CUSTOMER_ID, FIRST_NAME, LAST_NAME) AS
SELECT 1, 'Faith', 'Aaron' FROM DUAL UNION ALL
SELECT 2, 'Lisa', 'Saladino' FROM DUAL UNION ALL
SELECT 3, 'Micheal', 'Mazzarone' FROM DUAL UNION ALL
SELECT 4, 'Joseph', 'Zanzone' FROM DUAL UNION ALL
SELECT 5, 'Sandy', 'Herring' FROM DUAL;
ALTER TABLE customers
ADD CONSTRAINT customers_pk PRIMARY KEY (customer_id);
CREATE TABLE items
(PRODUCT_ID, PRODUCT_NAME, PRICE) AS
SELECT 100, 'Black Shoes', 79.99 FROM DUAL UNION ALL
SELECT 101, 'Brown Pants', 111.99 FROM DUAL UNION ALL
SELECT 102, 'White Shirt', 10.99 FROM DUAL;
ALTER TABLE items
ADD CONSTRAINT items_pk PRIMARY KEY (product_id);
create table purchases(
ORDER_ID NUMBER GENERATED BY DEFAULT AS IDENTITY (START WITH 1) NOT NULL,
customer_id number,
PRODUCT_ID NUMBER,
QUANTITY NUMBER,
purchase_date timestamp
);
ALTER TABLE purchases
ADD CONSTRAINT order_pk PRIMARY KEY (order_id);
ALTER TABLE purchases ADD CONSTRAINT customers_fk FOREIGN KEY (customer_id) REFERENCES customers(customer_id);
ALTER TABLE purchases ADD CONSTRAINT items_fk FOREIGN KEY (PRODUCT_ID) REFERENCES items(product_id);
insert into purchases (customer_id, product_id, quantity, purchase_date)
SELECT 3, 102, 4,TIMESTAMP '2022-12-22 21:44:35' + NUMTODSINTERVAL ( LEVEL * 2, 'DAY') FROM dual
CONNECT BY LEVEL <= 15 UNION ALL
select 1, 101,3, date '2023-03-29' + level * interval '2' day from dual
connect by level <= 12
union all
select 2, 101,2, date '2023-01-15' + level * interval '8' hour from dual
connect by level <= 15
union all
select 2, 102,2,date '2023-04-13' + level * interval '1 1' day to hour from dual
connect by level <= 11
union all
select 3, 101,2, date '2023-02-01' + level * interval '1 05:03' day to minute from dual
connect by level <= 10
union all
select 3, 101,1, date '2023-04-22' + level * interval '23' hour from dual
connect by level <= 23
union all
select 3, 100,1, date '2022-03-01' + level * interval '1 00:23:05' day to second from dual
connect by level <= 15
union all
select 4, 102,1, date '2023-01-01' + level * interval '5' hour from dual
connect by level <= 60;
SELECT
customer_id,
/*
q.first_name,
q.last_name,
*/
Num_Orders,
purchase_date AS Last_Purchase_Date,
order_id AS Last_Order_ID
FROM (
SELECT p.*,
COUNT( order_id ) OVER ( PARTITION BY customer_id ) AS Num_Orders,
ROW_NUMBER() OVER ( PARTITION BY customer_id ORDER BY purchase_date DESC,
order_id DESC ) AS rn
FROM purchases p
) q
/*
join purchases p on q.customer_id = p.customer_id
*/
WHERE rn = 1
ORDER BY customer_id;
一个选择是
systimestamp 中减去上次购买日期（实际上是 时间戳）并从中提取天数
SQL> with last_purchase_per_customer as
2 (select p.customer_id, max(p.purchase_date) max_purchase_date
3 from purchases p
4 group by p.customer_id
5 )
6 select c.customer_id, c.first_name, c.last_name, p.max_purchase_date,
7 extract(day from (systimestamp - p.max_purchase_date)) as number_of_days
8 from customers c left join last_purchase_per_customer p on p.customer_id = c.customer_id
9 order by c.customer_id;
CUSTOMER_ID FIRST_N LAST_NAME MAX_PURCHASE_DATE NUMBER_OF_DAYS
----------- ------- --------- ---------------------------------- --------------
1 Faith Aaron 22-APR-2023 00:00:00.000000 105
2 Lisa Saladino 24-APR-2023 11:00:00.000000 103
3 Micheal Mazzarone 14-MAY-2023 01:00:00.000000 83
4 Joseph Zanzone 13-JAN-2023 12:00:00.000000 204
5 Sandy Herring
SQL>
[编辑] 如果您想获取任意数量的最后交易，请修改 CTE 以按购买日期按降序排列每个客户，然后 - 在主查询中 - 仅获取所需数量的交易。还有额外的
whereor p.rnk is nullSQL> with purchases_per_customer as
2 (select p.customer_id,
3 p.purchase_date,
4 rank() over (partition by p.customer_id order by p.purchase_date desc) rnk
5 from purchases p
6 )
7 select c.customer_id, c.first_name, c.last_name, p.purchase_date,
8 extract(day from (systimestamp - p.purchase_date)) as number_of_days
9 from customers c left join purchases_per_customer p on p.customer_id = c.customer_id
10 where p.rnk <= &par_number_of_transactions
11 or p.rnk is null
12 order by c.customer_id, p.purchase_date desc;
Enter value for par_number_of_transactions: 3
CUSTOMER_ID FIRST_NAME LAST_NAME PURCHASE_DATE NUMBER_OF_DAYS
----------- ----------- --------- ----------------------------------- --------------
1 Faith Aaron 22-APR-2023 00:00:00.000000 106
1 Faith Aaron 20-APR-2023 00:00:00.000000 108
1 Faith Aaron 18-APR-2023 00:00:00.000000 110
2 Lisa Saladino 24-APR-2023 11:00:00.000000 104
2 Lisa Saladino 23-APR-2023 10:00:00.000000 105
2 Lisa Saladino 22-APR-2023 09:00:00.000000 106
3 Micheal Mazzarone 14-MAY-2023 01:00:00.000000 84
3 Micheal Mazzarone 13-MAY-2023 02:00:00.000000 85
3 Micheal Mazzarone 12-MAY-2023 03:00:00.000000 86
4 Joseph Zanzone 13-JAN-2023 12:00:00.000000 205
4 Joseph Zanzone 13-JAN-2023 07:00:00.000000 205
4 Joseph Zanzone 13-JAN-2023 02:00:00.000000 205
5 Sandy Herring
13 rows selected.
SQL>