New feature of MySQL8 - window function

MySQL 8.0 supports window functions (Window Function), also known as analytical functions. Window functions are similar to group-by aggregate functions, but produce one result per row of data. Aggregate window functions: SUM /AVG / COUNT /MAX/MIN etc.

The case is as follows: the sales table structure and data are as follows:

Common grouping, aggregation (statistics by country)

SELECT country,sum(sum)
FROM sales
GROUP BY country
order BY country;

Window functions (summarized by country)

select year,country,product,sum,
    sum(sum) over (PARTITION by country) as country_sum
 from sales
order by country,year,product,sum;

Window function (calculates the tie value)

select year,country,product,sum,
            sum(sum) over (PARTITION by country) as country_sum,
            avg(sum) over (PARTITION by country) as country_avg
 from sales
order by country,year,product,sum;

Dedicated window functions:

Serial number functions: ROW_NUMBER(), RANK(), DENSE_RANK()
Distribution functions: PERCENT_RANK(), CUME_DIST()
Front and back functions: LAG(), LEAD()
Head and tail functions: FIRST_VALUE(), LAST_VALUE()
Other functions: NTH_VALUE(), NTILE()

window function (ranking)

A ranking window function for calculating category rankings, and a value window function for obtaining data at a specified location

SELECT
    YEAR,
    country,
    product,
    sum,
    row_number() over (ORDER BY sum) AS 'rank',
        rank() over (ORDER BY sum) AS 'rank_1'
FROM
    sales;

SELECT
    YEAR,
    country,
    product,
    sum,
    sum(sum) over (PARTITION by country order by sum rows unbounded preceding) as sum_1
FROM
    sales order by country,sum;

Of course, there are many operations that can be done, see the official website for details:

https://dev.mysql.com/doc/refman/8.0/en/window-function-descriptions.html

New feature of MySQL8 - window function

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