PostgreSQL solution where the timestamp is not automatically updated when the table is updated

  • 2020-05-06 11:56:45
  • OfStack

The solution is that the timestamp is not automatically updated when PostgreSQL updates a table, as shown in

Operating system: CentOS 7.3.1611_x64

PostgreSQL version: 9.6

problem description

The ability to automatically time when PostgreSQL executes Insert statements can be implemented when a table is created, but the timestamp is not automatically updated when the table is updated.

In mysql, you can define auto-update fields when you create a table, such as

create table ab (
 id int,
 changetimestamp timestamp

So how does PostgreSQL work?


Through the trigger implementation, as follows:

create or replace function upd_timestamp() returns trigger as
  new.modified = current_timestamp;
  return new;
language plpgsql;

drop table if exists ts;
create table ts (
  id   bigserial primary key,
  tradeid integer ,
  email varchar(50),
  num integer,
  modified timestamp default current_timestamp
create trigger t_name before update on ts for each row execute procedure upd_timestamp();

Test code:

insert into ts (tradeid,email,num) values (1223,'',1);
update ts set email='Mike_Zhang@live' where tradeid = 1223 ;

create unique index ts_tradeid_idx on ts(tradeid);
insert into ts(tradeid,email,num) values (1223,'',2) on conflict(tradeid) do update
set email =,num=excluded.num;

select * from ts;
-- delete from ts;

Ok, that's all, I hope it helped you.

The github address for this article.

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