question about altering date column in table with postgresSQL

i created table with 4column with

create table conversation(
    user_name varchar(200),
    employer_name varchar(200),
    message text,
    date_sent timestamp
)

now i want alter date_sent column without remove it i want to set default value of current_timestamp for this column what i must do

>Solution :

You can use

LTER TABLE conversation ALTER COLUMN  
date_sent SET DEFAULT current_timestamp;

create table conversation(
user_name varchar(200), 
employer_name varchar(200), 
message text, 
date_sent timestamp );

ALTER TABLE conversation ALTER COLUMN  
date_sent SET DEFAULT current_timestamp;

insert into conversation 
(user_name) values
('me');

select * from conversation;

user_name | employer_name | message | date_sent                 
:-------- | :------------ | :------ | :-------------------------
me        | null          | null    | 2022-04-01 09:38:13.674547

db<>fiddle here