MySQL 5.7

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create table game(
id int,
dur int, 
duration int
GENERATED ALWAYS AS (case when dur > 65000 then dur /1000 else dur end) STORED)
insert into game (id, dur) values
(1,1000),
(2,100000);

Records: 2  Duplicates: 0  Warnings: 0


select * from game;


id
dur
duration


1
1000
1000

2
100000
100