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Xiaobai learns MySQL - incremental statistical SQL requirements - windowing function scheme

2022-06-29 13:37:00 【bisal(Chen Liu)】

《 Xiaobai studies MySQL - Incremental Statistics SQL The needs of 》 in , We mentioned a MySQL Incremental statistical requirements SQL, In fact, it is not just the scheme used in the text , There will be others , Many friends mentioned that you can use MySQL 8.0 Supported windowing functions to solve .

Oracle Window function is supported in ,MySQL It's from 8.0 Start supported , Official documents ,

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

The role of the windowing function , Data before aggregation can be displayed , It can also display the aggregated data .

Review the original test data , The test table tt There are three fields ,code Is the identification name ,cdate Is the corresponding date ,ctotal It's a statistic ,

If you use the windowing function directly ,

select code, date_format(cdate, '%Y-%m'), 
ctotal,
sum(ctotal) 
over (partition by code, date_format(cdate, '%Y-%m')
order by date_format(cdate, '%Y-%m')) as total
from tt;

Although according to cdate It's done partition by, But because of cdate The storage is not only to " month ", No clustering , So even if according to "%Y-%m", It shows several ,

You can remove the weight , Meet our needs ,

select t.code, t.cdate, t.total, 
sum(t.total) over (partition by t.code order by t.cdate) as g_total
from 
(select code, date_format(cdate, '%Y-%m') as cdate, 
ctotal,
row_number() over (partition by code, date_format(cdate, '%Y-%m') 
order by code, date_format(cdate, '%Y-%m')) as r_seq,
sum(ctotal) 
over (partition by code, date_format(cdate, '%Y-%m') 
order by code, date_format(cdate, '%Y-%m')) as total
from tt) t
where t.r_seq = 1;

With the help of row_number() function , Take out the only record of each month , And then by executing partition by, Incremental accumulation is realized ,

Write according to your needs SQL, There are often many ways to write , Although the same path leads to the same goal , But if we consider the performance 、 concise 、 Easy to understand and other factors , Will be very different . If you have a better solution , Welcome private message , Learn from others .

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