Laravel eloquent find max(date) with additional search criteria - php

Question

I'm trying to figure out the best way to retrieve results from the database such that the created_at is the most recent, and also checking that another value (in this case Temps->value) matches a specific criteria..
For example (some information abbreviated)
LOCATIONS
+----+---------+
| ID | CITY |
+----+---------+
| 1 | DALLAS |
| 2 | CHICAGO |
| 3 | ATLANTA |
+----+---------+
TEMPS
+----+-------+----------+------------+
| ID | VALUE | CITY_ID | CREATED_AT |
+----+-------+----------+------------+
| 1 | 70 | 1 | 2010 |
| 2 | 95 | 1 | 2015 |
| 3 | 90 | 2 | 2010 |
| 4 | 80 | 2 | 2015 |
| 5 | 99 | 3 | 2015 |
+----+-------+----------+------------+
my location model.
class Location extends model
{
...
public function latestValue()
{
return $this->hasOne('App\Temp')->latest();
}
In this case I would only like the Locations in which the latest temperature reading is > 90..
In my controller if have
$highTemps = Location::with('latestValue')->get();
without iterating through every city explicitly, is there a way to adjust my eloquent relationship, or even use a collection method to filter the results?
I've looked at filter() but I'm not sure how to use that on a relationship. Especially if you're trying to filter 2-3 relationships deep. (imagine I'm starting off with Country->states->locations->temps->latestValue etc)
It would be great to have the initial query filter the results. But I can't figure out the combination of groupBy() and max() and having() etc to make the eloquent statement work.

Answer 1

I think the Relationship you are establishing, it's wrong..
The Problem is very simple if the relationship hasMany() will be used..
First all the latest entries will be fetched , followed by filtering the max out of them.
class Location extends model
{
...
public function latestValue()
{
return $this->hasMany('App\Temp')->latest();
}
rest is not that much typical i assume.