MySQL + PHP - Querying relative format dates - php

Question

I have two tables: steps and flows.
steps has many flows.
steps has relative_time (string) column.
flows has active_on (nullable, timestamp) column.
Steps relative_time stores relative formats and their values looks like: "+1 year", "+2 days", "+30 days", etc.
Flows active_on is set when a flow gets activated by user and it looks like: "2017-12-30 00:00:00".
Every time I want to know when a flow will expire, I select it from database and, in PHP (Laravel, Carbon), I execute:
/**
* #return null|Carbon
*/
public function getExpiresAtAttribute()
{
if (!$this->active_on) {
return null;
}
// Access the relative time for step (for example: "+3 days").
$relativeTime = $this->step->relative_time;
// Adds the limit time to the activation date,
// turning it possible to check when the current flow
// will "expires".
return $this->active_on->modify($relativeTime);
}
Problem
It's easy to check expires at value in PHP. The problem is that now I need to select only flows that are "expired" directly from database and I don't know if it is possible by using this approach. How can I achieve this?

Answer 1

You could store in relative_time the number of days, instead of the php date interval. This way you can query:
SELECT * FROM flows, steps WHERE flows.step_id = step.id AND NOW() > ADDDATE(flows.active_on, steps.relative_time)
This way you get all the flows expired.
No need to change database structure actually. You could create a migration to transform relative_time from dateinterval to number of days (is a string field).
foreach (Steps::all() as $step) {
$step->update([
'relative_time' => strtotime($step->relative_time,0)/(3600*24);
]);
}
Then you can adjust the getExpiresAtAttribute:
/**
* #return null|Carbon
*/
public function getExpiresAtAttribute()
{
if (!$this->active_on) {
return null;
}
// Access the relative time for step (for example: "+3 days").
$relativeTime = $this->step->relative_time;
// Adds the limit time to the activation date,
// turning it possible to check when the current flow
// will "expires".
return $this->active_on->modify("+$relativeTime days");
}