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
桀桀桀桀桀桀10 分钟前
数据库中的用户管理和权限管理
数据库·mysql
lzhlizihang1 小时前
【Hive sql 面试题】求出各类型专利top 10申请人,以及对应的专利申请数(难)
大数据·hive·sql·面试题
superman超哥1 小时前
04 深入 Oracle 并发世界:MVCC、锁、闩锁、事务隔离与并发性能优化的探索
数据库·oracle·性能优化·dba
用户8007165452001 小时前
HTAP数据库国产化改造技术可行性方案分析
数据库
engchina2 小时前
Neo4j 和 Python 初学者指南:如何使用可选关系匹配优化 Cypher 查询
数据库·python·neo4j
engchina2 小时前
使用 Cypher 查询语言在 Neo4j 中查找最短路径
数据库·neo4j
尘浮生2 小时前
Java项目实战II基于Spring Boot的光影视频平台(开发文档+数据库+源码)
java·开发语言·数据库·spring boot·后端·maven·intellij-idea
威哥爱编程2 小时前
SQL Server 数据太多如何优化
数据库·sql·sqlserver
小华同学ai2 小时前
AJ-Report:一款开源且非常强大的数据可视化大屏和报表工具
数据库·信息可视化·开源
Acrelhuang3 小时前
安科瑞5G基站直流叠光监控系统-安科瑞黄安南
大数据·数据库·数据仓库·物联网