postgresql兼容MySQL on update current_timestamp

问题描述

PostgreSQL执行Insert语句时，自动填入时间的功能可以在创建表时实现，但更新表时时间戳不会自动自动更新。

在mysql中可以在创建表时定义自动更新字段，比如 ：

create table ab (
id int,
changetimestamp timestamp
NOT NULL
default CURRENT_TIMESTAMP
on update CURRENT_TIMESTAMP
);
那PostgreSQL中怎么操作呢？

解决方案

通过触发器实现，具体如下：

create or replace function upd_timestamp() returns trigger as
$$
begin
    new.modified = current_timestamp;
    return new;
end
$$
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();

测试代码：
insert into ts (tradeid,email,num) values (1223,‘[e-mail]’,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,‘[e-mail]’,2) on conflict(tradeid) do update
//set email = excluded.email,num=excluded.num;

select * from ts;
– delete from ts;