Is it possible to create a column with a UNIX_TIMESTAMP default in MySQL?

database, database-design, database-schema, mysql, sql

Solution

The way MySQL implements the `TIMESTAMP` data type, it is actually storing the epoch time in the database. So you could just use a `TIMESTAMP` column with a default of `CURRENT_TIMESTAMP` and apply the `UNIX_TIMESTAMP()` to it if you want to display it as an int:

CREATE TABLE foo(
  created TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);

insert into foo values (current_Date()),(now());

select unix_timestamp(created) from foo;
+-------------------------+
| unix_timestamp(created) |
+-------------------------+
|              1300248000 |
|              1300306959 |
+-------------------------+
2 rows in set (0.00 sec)

However, if you really want the datatype of the column to be `INT`, you can use R. Bemrose's suggestion and set it via trigger:

CREATE TABLE foo(
  created INT NULL
);

delimiter $$

create trigger tr_b_ins_foo before insert on foo for each row
begin
  if (new.created is null)
  then
    set new.created = unix_timestamp();
  end if;
end $$

delimiter ;


insert into foo values (unix_timestamp(current_Date())), (null);

select created from foo;
+------------+
| created    |
+------------+
| 1300248000 |
| 1300306995 |
+------------+
2 rows in set (0.00 sec)

Problem

I'm trying to do this, but it seems like MySQL isn't allowing me. Is there a solution to this issue or am I expected to always include the function in my INSERT queries? ``` CREATE TABLE foo( created INT NOT NULL DEFAULT UNIX_TIMESTAMP() ) ``` I'm aware of the TIMESTAMP type that accepts a CURRENT_TIMESTAMP default, but my client insisted on using epoch time in the database.

Original source