SQL 选择数据并按日期范围对数据进行分组

Question

我有这样的数据表

<头>

价格	日期	类型
1000	2021-03-13	A
1000	2021-03-14	A
1000	2021-03-15	A
1300	2021-03-16	A
1000	2021-03-17	A
1300	2021-03-18	A
1000	2021-03-19	A
1500	2021-03-20	A
1500	2021-03-21	A
1500	2021-03-22	A
2000	2021-03-13	B
2000	2021-03-14	B
2000	2021-03-15	B
2000	2021-03-16	B
2000	2021-03-17	B

我想查询这样的数据

<头>

价格	开始日期	结束日期	类型
1000	2021-03-13	2021-03-15	A
1300	2021-03-16	2021-03-16	A
1000	2021-03-17	2021-03-17	A
1300	2021-03-18	2021-03-18	A
1000	2021-03-19	2021-03-19	A
1500	2021-03-20	2021-03-22	A
2000	2021-03-13	2021-03-17	B

我当前的sql如下，但根本不正确

SELECT MIN(date) as startDate, MAX(date) as endDate, price, type                                      
                            FROM prices 
                            GROUP BY type, price
                            ORDER BY type, MIN(date)

Answer 1

这是一个间隙和孤岛问题，一种简单的处理方法是使用行数差异方法。假设您使用的是 MySQL 8+，以下应该可以工作：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY type ORDER BY date) rn1,
              ROW_NUMBER() OVER (PARTITION BY type, price ORDER BY date) rn2
    FROM prices
)

SELECT price, MIN(date) AS startDate, MAX(date) AS endDate, type
FROM cte
GROUP BY price, type, rn1 - rn2
ORDER BY type, startDate;

Demo

Answer 2

如果不使用 CTE，您可以使用以下查询：

SELECT w1.price, w1.date, w2.date, w1.type FROM
(
  SELECT * FROM mytable t1
  WHERE NOT EXISTS (
    SELECT 1 FROM mytable t2
    WHERE 
      t1.price = t2.price AND
      t1.type = t2.type AND
      DATEDIFF(t2.date, t1.date) = -1
  )
) w1
INNER JOIN
(
  SELECT * FROM mytable t1
  WHERE NOT EXISTS (
    SELECT 1 FROM mytable t2
    WHERE 
      t1.price = t2.price AND
      t1.type = t2.type AND
      DATEDIFF(t2.date, t1.date) = +1
  )
) w2
ON
w1.price = w2.price AND
w1.type = w2.type AND
w1.date <= w2.date AND
NOT EXISTS (
  SELECT * FROM mytable t1
  WHERE NOT EXISTS (
    SELECT 1 FROM mytable t2
    WHERE 
      t1.price = t2.price AND
      t1.type = t2.type AND
      DATEDIFF(t2.date, t1.date) = +1
  )
  AND
  w1.price = t1.price AND
  w1.type = t1.type AND
  w1.date <= t1.date AND t1.date < w2.date
)

1. 获取每个时期的较小和较大日期。
2. 加入这些表。
3. 获取较小日期和较大日期之间的行。

DB Fiddle

Answer 3

SELECT MIN(date) as startDate, MAX(date) as endDate, price, type    
FROM prices
GROUP BY type, price
ORDER BY MIN(date) ASC

此查询可能适用于按日期升序排列数据