Analysis function (window function) in mysql

Everyone knows that the analysis function of Oracle is very useful for complicated statistics, but Mysql does not support the analysis function of Oracle (window function), so please refer the below solution.

create table audit_test(
 user_id int,
 create_date date,
 income int
);
 
insert into audit_test values(1,’2020–03–01',100);
insert into audit_test values(1,’2020–03–02',300);
insert into audit_test values(1,’2020–03–03',200);
insert into audit_test values(1,’2020–03–04',500);
insert into audit_test values(1,’2020–03–05',500);
 
insert into audit_test values(2,’2020–03–01',200);
insert into audit_test values(2,’2020–03–02',300);
insert into audit_test values(2,’2020–03–03',300);
insert into audit_test values(2,’2020–03–04',500);
insert into audit_test values(2,’2020–03–05',400);
 
select it.user_id, 
 it.create_date, 
 it.income,
 case
 when @preVal = it.user_id then @curVal := @curVal + it.income
 when @preVal := it.user_id then @curVal := it.income
 end AS sum_income
from audit_test it, (select @preVal:=null, @curVal:=null) r
order by it.user_id asc, it.create_date asc;

Observations:

1. User variables, true only for the current client, are @preVal and @curVal;

2. (pick @preVal:=null, @curVal:=null) r Initialize the variables @preVal and @curVal;

2. The second is only used as an assignment to @preVal, implying that the condition is still valid. (“, 0, and null are all wrong in mysql);

The use of similar analysis functions (windowing functions) in mysql is described above. Correct me, please.

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