MySQL8.0版本如何正确的使用窗口函数详解

SELECT 
	<窗口函数名> over (partition by <分组列名> order by <排序列名>)
FROM `你的表名` 

SELECT 
	<窗口函数名> OVER win
FROM `你的表名` 
WINDOW win AS (partition by <分组列名> order by <排序列名>)

# 添加over子句
SUM([DISTINCT] expr) [over_clause]

SELECT 
     country, 
     SUM(profit) AS country_profit
FROM sales
GROUP BY country
ORDER BY country;

SELECT
     year, country, product, profit,
     SUM(profit) OVER() AS total_profit,
     SUM(profit) OVER(PARTITION BY country) AS country_profit
FROM sales
ORDER BY country, year, product, profit;

SELECT
     val,
     ROW_NUMBER()   OVER w AS 'row_number',
     CUME_DIST()    OVER w AS 'cume_dist',
     PERCENT_RANK() OVER w AS 'percent_rank'
FROM numbers
WINDOW w AS (ORDER BY val);

 SELECT
      time, subject, val,
      FIRST_VALUE(val)  OVER w AS 'first',
      LAST_VALUE(val)   OVER w AS 'last',
      NTH_VALUE(val, 2) OVER w AS 'second',
      NTH_VALUE(val, 4) OVER w AS 'fourth'
FROM observations
WINDOW w AS (PARTITION BY subject ORDER BY time ROWS UNBOUNDED PRECEDING);

SELECT
    t, val,
    LAG(val)        OVER w AS 'lag',
    LEAD(val)       OVER w AS 'lead',
    val - LAG(val)  OVER w AS 'lag diff',
    val - LEAD(val) OVER w AS 'lead diff'
FROM series
WINDOW w AS (ORDER BY t);

SELECT
     val,
     ROW_NUMBER() OVER w AS 'row_number',
     NTILE(2)     OVER w AS 'ntile2',
     NTILE(4)     OVER w AS 'ntile4'
FROM numbers
WINDOW w AS (ORDER BY val);

SELECT
     val,
     ROW_NUMBER() OVER w AS 'row_number',
     RANK()       OVER w AS 'rank',
     DENSE_RANK() OVER w AS 'dense_rank'
FROM numbers
WINDOW w AS (ORDER BY val);