用 SQL 找出某只股票连续上涨的最长天数

涉及多张中间表:

sql 复制代码
SELECT MAX(consecutive_day)
FROM (SELECT COUNT(*) as consecutive_day
  FROM (SELECT trade_date, SUM(rise_mark) OVER (ORDER BY trade_date) AS days_no_gain
     FROM (SELECT trade_date,
                CASE
                    WHEN closing_price > LAG(closing_price) OVER (ORDER BY trade_date)
                         THEN 0
                    ELSE 1 END AS rise_mark
           FROM stack_price) subquery1) subquery2
  GROUP BY days_no_gain) subquery3;

Over 语法

sql 复制代码
SELECT
  product_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
FROM
  sales;

basic:

sql 复制代码
order_id | customer_id | order_amount
-------------------------------------
1        | 1           | 100
2        | 1           | 150
3        | 2           | 200
4        | 2           | 50
5        | 2           | 120

result:

sql 复制代码
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.

OLAP / OLTP

SQL 作为查询语言而发明, 名字叫 "结构化查询"(structured query), 数学基础是 "关系模型", 没有考虑复杂计算 (与之相对的是离散数学, 把 "数据存储 + 数据计算" 做在一起)

近年来, 数据处理和计算的需求越来越大, 于是 OLAP(联机分析处理)和 OLTP(联机事务处理)的概念就诞生了.

  • OLAP: Online Analytical Processing.
  • OLTP: Online Transaction Processing.

它们基于数据库, 属于"数据库 + 计算层".

处理海量数据, 有效率瓶颈.

相关推荐
TDengine (老段)1 分钟前
TDengine 数学函数 RAND 用户手册
java·大数据·数据库·物联网·时序数据库·tdengine·涛思数据
野犬寒鸦12 分钟前
从零起步学习MySQL || 第十章:深入了解B+树及B+树的性能优势(结合底层数据结构与数据库设计深度解析)
java·数据库·后端·mysql·1024程序员节
GZ_TOGOGO17 分钟前
Oracle OCP考试报名常见问题详解
数据库·oracle·ocp认证
睡不醒的猪儿17 分钟前
nginx日志同步阿里云datahub后写入数据库
数据库·nginx·阿里云
xie_zhr33 分钟前
【PB案例学习笔记】-46在数据窗口中编辑数据
数据库·his·1024程序员节·干货分享·pb·powerbuilder
小小的木头人1 小时前
Redis 集群安装指南
数据库·redis
星空的资源小屋1 小时前
Antares SQL,一款跨平台开源 SQL 客户端
数据库·人工智能·pdf·开源·电脑·excel·1024程序员节
2301_800256111 小时前
地理空间数据库作业笔记——查询最偏僻的城市
数据库·笔记·sql·postgresql·1024程序员节
卓码软件测评2 小时前
软件可用性测试历史概念✅软件可用性测试的国际标准✅软件可用性测试方法
数据库·单元测试·可用性测试·软件需求
R.lin2 小时前
OSS服务模块-基于数据库配置的Java OSS服务解决方案,支持MinIO、七牛云、阿里云和腾讯云
java·数据库·后端·mysql