用 SQL 找出某只股票连续上涨的最长天数

涉及多张中间表:

SELECT MAX(consecutive_day)
FROM (SELECT COUNT(*) as consecutive_dayFROM (SELECT trade_date, SUM(rise_mark) OVER (ORDER BY trade_date) AS days_no_gainFROM (SELECT trade_date,CASEWHEN closing_price > LAG(closing_price) OVER (ORDER BY trade_date)THEN 0ELSE 1 END AS rise_markFROM stack_price) subquery1) subquery2GROUP BY days_no_gain) subquery3;

Over 语法

SELECTproduct_id,sale_date,sale_amount,SUM(sale_amount) OVER (PARTITION BY product_id ORDER BY sale_date) AS total_sales,SUM(sale_amount) OVER (PARTITION BY product_id) AS running_total
FROMsales;

basic:

order_id | customer_id | order_amount
-------------------------------------
1        | 1           | 100
2        | 1           | 150
3        | 2           | 200
4        | 2           | 50
5        | 2           | 120

result:

order_id | customer_id | order_amount | total_amount | running_total
-------------------------------------------------------------------
1        | 1           | 100          | 100          | 250
2        | 1           | 150          | 250          | 250
3        | 2           | 200          | 200          | 370
4        | 2           | 50           | 250          | 370
5        | 2           | 120          | 370          | 370

Window function

A window function is a type of function in SQL that performs calculations across a set of rows called a “window.” The window is defined by the OVER clause, which specifies the partitioning and ordering of the rows.

SUM(order_amount) OVER (PARTITION BY customer_id ORDER BY order_id):

SUM(order_amount): This is the window function itself, in this case, the SUM function is used to calculate the sum of the order_amount.
OVER: It introduces the window function and specifies the window’s characteristics.
PARTITION BY customer_id: This clause divides the rows into separate partitions based on the customer_id. Each partition will have its own calculation of the sum.
ORDER BY order_id: This clause determines the order in which the rows are processed within each partition. In this case, it orders the rows by the order_id.
SUM(order_amount) OVER (PARTITION BY customer_id):

This is another usage of the SUM window function, but without specifying the ordering using ORDER BY. Without the ORDER BY clause, the entire partition is considered, and the calculation is performed on all rows with the same customer_id.
The window function, in combination with the OVER clause, allows us to perform calculations within specific partitions and orderings defined by the columns specified. It provides a way to aggregate or calculate values based on a subset of rows without collapsing the result set or using subqueries.

Other common window functions include ROW_NUMBER(), AVG(), MIN(), MAX(), and LEAD()/LAG(), among others. Each function has its own specific purpose and behavior within the window frame defined by the OVER clause.