从某个月开始，使用12个月的时间周期对日期进行迭代

Question

DB Fiddle

CREATE TABLE customers (
id SERIAL PRIMARY KEY,
order_date DATE,
customer VARCHAR(255)
);
INSERT INTO customers
(order_date, customer)
VALUES 
('2020-05-10', 'user_01'),
('2020-05-15', 'user_01'),
('2020-05-18', 'user_02'),
('2020-05-26', 'user_03'),
('2020-06-03', 'user_04'),
('2020-06-05', 'user_05'),
('2020-06-24', 'user_06'),

('2021-05-02', 'user_01'),
('2021-05-05', 'user_01'),
('2021-05-12', 'user_03'),
('2021-05-20', 'user_07'),
('2021-06-08', 'user_04'),
('2021-06-20', 'user_06'),
('2021-06-21', 'user_08'),
('2021-06-25', 'user_08'),
('2021-06-25', 'user_09');

预期结果：

order_date   |   customer  |  
-------------|-------------|----
2021-05-02   |   user_01   |  
2021-05-05   |   user_01   |  
2021-05-12   |   user_03   |  
-------------|-------------|----
2021-06-08   |   user_04   |  
2021-06-20   |   user_06   |  

---

我想列出某个月内的所有客户

a( 在过去的12个月内是否存在，以及
b(在之前已经存在这段的12个月

---

对于单月我可以通过使用以下查询来实现这一点：

SELECT
c1.order_date,
c1.customer
FROM customers c1
WHERE c1.order_date BETWEEN '2021-05-01 00:00:00' AND '2021-05-31 23:59:59'
/* Check if customer exists in the past 12 months */
AND NOT EXISTS
(SELECT
c2.customer
FROM customers c2
WHERE c2.order_date BETWEEN '2020-06-01 00:00:00' AND '2021-04-30 23:59:59'
AND c2.customer = c1.customer)
/* Check if customer exists before the past 12 months */
AND EXISTS
(SELECT
c2.customer
FROM customers c2
WHERE c2.order_date < '2020-06-01 00:00:00'
AND c2.customer = c1.customer)
ORDER BY 2;

---

但是，我必须分别为每个月运行此查询

因此，我想知道是否有一个迭代解决方案可以同时通过多个月

在上面的例子中，它将运行BETWEEN '2021-05-01 00:00:00' AND '2021-06-30 23:59:59'，并从5月开始计算12个月，在下一步中从6月开始计算，以获得预期结果。

你知道这是否可能吗？

Answer 1

SELECT 
t1.order_date, 
t1.customer
FROM 
(SELECT
c.customer,
c.order_date,
LAG(c.order_date) OVER (PARTITION BY c.customer ORDER BY c.order_date) AS prev_order_date
FROM customers c) t1
WHERE t1.order_date BETWEEN '2021-05-01' AND '2021-06-30' 
AND t1.prev_order_date >= date_trunc('month', t1.order_date) - interval '12 month'
AND t1.prev_order_date < date_trunc('month', t1.order_date)
ORDER BY 1,2;

DB Fiddle