Postgres 12

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select version();

version

PostgreSQL 12.17 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-20), 64-bit

SELECT 1

create table my_table ( id           serial 
                      , cola         text
                      , when_time    time  default now()::time   
                      ) ;
insert into my_table (cola) 
     ( values ('abc'), ('xyz') );

CREATE TABLE

INSERT 0 2

select * from my_table;

id
cola
when_time

1
abc
14:41:22.343396

2
xyz
14:41:22.343396

SELECT 2

ALTER TABLE my_table ADD COLUMN open_h text
GENERATED ALWAYS AS (cola || 'ok') STORED

ALTER TABLE

select * from my_table

id
cola
when_time
open_h

1
abc
14:41:22.343396
abcok

2
xyz
14:41:22.343396
xyzok

SELECT 2