Laravel Version: #.#.# 8.18.1
PHP Version: #.#.# 7.4
Database Driver & Version: MySQL 5.7.32
Description:
Had two models (menu, service) with two different databases, connection set in model. when I get menu model with (service) relation, it's working fine. But when used has(service) to get the menu which have service will shown
Base table or view not found: 1146 Table 'common.services' doesn't exist
it will look in my first database
common is my first database name and services are store in second database.
Steps to Reproduce:
create two model in different database
fetch menu with relation has(service) to get only menu which have service
Documentation
From Laravel Documentation :
Eloquent does not currently support querying for relationship
existence across databases. The relationships must exist within the
same database.
QueryBuilder VS Eloquent
What Cause success retrieve on with() and failure on has() ?
QueryBuilder crosses Databases
with() has been implemented in Illuminate\Database\Eloquent\Builder and collects relations in $eagerLoading array to load with query.
Relation has not implement cross Database Feature
but has() is in Illuminate\Database\Eloquent\Concerns\QueriesRelationships trait and adopted in Illuminate\Database\Eloquent\Relations\Relation calls getRelationWithoutConstraints() which is :
/**
* Get the "has relation" base query instance.
*
* #param string $relation
* #return \Illuminate\Database\Eloquent\Relations\Relation
*/
protected function getRelationWithoutConstraints($relation)
{
return Relation::noConstraints(function () use ($relation) {
return $this->getModel()->{$relation}();
});
}
as PHPDoc says, its just getting base query instance for has relation .
its a simple method JUST creating a simple Base Query based on getModel() query (parent query) and add it.
The solution can be achieve using DB::raw.
Related
I am very new to Laravel and quite confuse with the model and database thing. I understand that a model represent one table. So I created a model using artisan command without migration and it created the code as follow.
namespace App;
use Illuminate\Database\Eloquent\Model;
class RegCars extends Model
{
//
}
Since I have a different table name, so I add protected $table = 'regcars'; and assume that this model can now access the table by running query such as RegCars::where('user_id', $user_id); from controller. But I wasn't able to get anything by running it.
So I am wondering, how does this model able to run the query? Is the migration needed in order to do this? Is there still other area I need to set before I can run any query?
highly recommend to read docs or at least watch a tutorial.
what you get is a query build not a model or a collection of models. laravel(eloquent) doesnt exactly know what you want so you query database then get the data by methods that laravel gives you if assume you want a RegCars you need a method like first:
RegCars::where('user_id', $user_id)->first(); // now you have model
more info: https://laravel.com/docs/8.x/eloquent
Laravel Version: 5.5
PHP Version: 7+
Database Driver & Version: mysql 5.7+
Scenario:
I have a SaaS application that has flexible database structure, so its fields are bound to change, especially given it has a Json field (for any extra database structure to be created from client side of the application), including relationship based fields. so Account Table can have dynamically created employee_id field, and thus the need to access relationships dynamically
Problem:
I need to EagerLoad models based on this dynamic relationship. If I had something like this:
// Account Model
public function employee(){
return $this->belongsTo(App\Employee);
}
it would be easy. But what I have is this:
public function modelBelongsTo(){
return $this->belongsTo($dynamicClassName, $dynamicForeignKey);
}
Now if I eager load this, I'll get Account Model instance with related Employee on key modelBelongsTo. This is how Eloquent Names based on the function of eagerload. But after this I cannot use this function again to eagerload a second model because it'll just overwrite results on modelBelongsTo key.
Possible Solution Directions:
1) Can I Somehow change laravel's process to use a name I provide?
or
2) Can I write functions on the fly to overcome this so I'll write employee function on the fly?
or
3) Worst Case Scenario: I iterate over all records to rename their keys individually because I am using a pagination, it wouldn't that big of a deal to loop over 10 records.
Us a morph relationship
define the various dynamic classnames say
Employee
Boss
Morph works by having the related key and the table name stored in the parent table, it means to relate them you have to use a join or an orm and you cant have foreign key constraint on it as it links to different tables.
then have your account have morphs where
we have
Account
as top class
then we have
EmployeeAccount, BossAccount
which have their relation to boss and employee
then in Account have morphto relation call it specificAccount()
to which in its child morphs have the morph relation to Account
then add it to $with so to eager load them so when fetching account you could simply do
$account ->specificAccount
to get its morph child. which is nullable
This is totally dynamic such that if you have other classes in future you can just add and add the morph relationship. This may be applied to any reflection or runtime evaluated and loaded classes/code though it is not advisable to do this, as you can always edit code to create new functionality without affecting previous.
class Product extends Model
{
/**
* Table name
* #var string
*/
protected $table = 'products';
/**
* #return \Illuminate\Database\Eloquent\Relations\BelongsTo
*/
public function buyerSupplier()
{
return $this->belongsTo('App\Models\Buyer', 'buyer_id');
}
}
Above is example code, if I call $this->buyerSupplier()->get() will it run MySQL?
Please, someone, tell me how this Laravel relationship is working?
The answer is Yes Laravel runs mysql queries behind the scene, here is a brief description from Laravel Official documents,
Laravel's database query builder provides a convenient, fluent interface to creating and running database queries. It can be used to perform most database operations in your application and works on all supported database systems.
The Laravel query builder uses PDO parameter binding to protect your application against SQL injection attacks. There is no need to clean strings being passed as bindings.
And about the relationships queries Laravel uses Eloquent:
Eloquent relationships are defined as methods on your Eloquent model classes. Since, like Eloquent models themselves, relationships also serve as powerful query builders, defining relationships as methods provides powerful method chaining and querying capabilities.
And for more details about how to choose between relationships methods
read more from Laravel Official Documents
There's a missing link I fail to understand.
I use migrations to create database tables and I define the relationships there. meaning.. if I have a person table and a job table and I need a one to many relationship between the person and jobs, I'd have the job table contain a "person_id".
When I seed data or add it in my app, I do all the work of adding the records setting the *_id = values etc.
but somehow I feel Laravel has a better way of doing this.
if I define that one to many relationship with the oneToMany Laravel Eloquent suports:
in my Person model.....
public function jobs()
{
return $this->hasMany('Jobs);
}
what's done on the database level? how do I create the migration for such table? Is Laravel automagically doing the "expected" thing here? like looking for a Jobs table, and having a "person_id" there?
Yep, Laravel is doing what you guess in your last paragraph.
From the Laravel documentation for Eloquent Relationships (with the relevant paragraph in bold):
For example, a User model might have one Phone. We can define this
relation in Eloquent:
class User extends Model {
public function phone()
{
return $this->hasOne('App\Phone');
}
}
The first argument passed to the hasOne method is the name of the
related model. Once the relationship is defined, we may retrieve it
using Eloquent's dynamic properties:
$phone = User::find(1)->phone;
The SQL performed by this statement
will be as follows:
select * from users where id = 1
select * from phones where user_id = 1
Take note that Eloquent assumes the foreign key of the relationship based on the model name. In this case, Phone model is assumed to use a user_id foreign key.
Also note that you don't actually have to explicitly set the foreign key indexes in your database (just having those "foreign key" columns with the same data type as the parent key columns is enough for Laravel to accept the relationship), although you should probably have those indexes for the sake of database integrity.
There is indeed support to create foreign key relationships inside migration blueprints and it's very simple too.
Here is a simple example migration where we define a jobs table that has a user_id column that references the id column on users table.
Schema::create('jobs', function($table)
{
$table->increments('id');
$table->integer('user_id')->unsigned();
$table->foreign('user_id')->references('id')->on('users');
});
You can also use some other methods that laravel provides such as onDelete() or onUpdate
Of course to understand better the options that are available to you please read the documentation here.
Edit:
Keep in mind that Eloquent is just using fluent SQL wrapper and behind the scenes there are just raw sql queries, nothing magical is happening, fluent just makes your life a lot easier and helpers you write maintainable code.
Take a look here about the Query Builder and how it works and also, as #Martin Charchar stated , here about Eloquent and relationships.
I am trying to get related model however i cannot seem to find correct documention. In yii 1.x i can do $jobsprocess->category0, but yii 2.x tell me to do $jobsprocess->getCategory(). This does not return a model but an ActiveQuery. How can I return a model object?
In your query use $model = YourModel::find()->with(['category])->all().
All relations using the getRelation() functions can be access with the with() function, but without the get and lowercase first letter.
You can then access the relational data with $model->category.