MySQL 8.0

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create table t (
    id int auto_increment primary key,
    x int,
    t timestamp default now(),
    tt time generated always as (time(t))
)
insert into t (x)
    values (3), (4);

Records: 2  Duplicates: 0  Warnings: 0


select *
from t


id
x
t
tt


1
3
2023-12-12 00:13:30
00:13:30

2
4
2023-12-12 00:13:30
00:13:30