I have been looking into eloquent's source code to see how it manages building its data structure when eager loaded with one or more relationships specified but I have not been successful.
For instance:
User has many photos, and a photo belongs to a User
How does eloquent perform its SQL query?
Does it make multiple SQL? A query to get the user and then another one to get his/her photo, or does it perform a single query.
I am also interested to see the structure of the SQL, because I have tried lots of options and there is absolutely no way I could tell what tables each field belonged to because the returned result is just plain array of objects.
Laravel will create at least two queries when you'll try to use eager loading.
For example, this code:
$users = User::with('photos')->get();
Will produce two queries similar to these:
select * from `users` where `users`.`deleted_at` is null
select * from `photos` where `photos`.`user_id` in ('1', '2', ... '99')
I'd recommend you to use Laravel Debugbar, if you want to better understand how raw SQL queries look like.
Sometimes using toSql() in php artisan tinker tool is also helpful:
\App\User::where('id', 2)->toSql()
Related
Curious if I constructed and tracked this m2m relationship correctly. Seems strange that every object in those arrays are named "user": {...} or "pip": {...}
Seems like these both should work
Update with screenshots:
Users table relationships:
Pips table relationships:
There's currently no automatic way to "hide" the join table from the GraphQL query and response. You need to traverse through the join table to get back the results you want from both directions so you can't avoid it using the default generated API.
It is possible to extend the GraphQL API using SQL Views if you want to try and "flatten" things from the perspective of people consuming this data.
Alternatively, I'd recommend calling the relationship something different to make it obvious that you're navigating through a join table. I'd recommend actually calling the relationship user_pips instead of pips as it makes it more clear what you're actually retrieving.
Category Table
Service Table
Branch Table
I have 3 tables link together. Above is my code, I want to produce the result same as below. Can I use a line of code to do that?
Or I have to get result from 2 tables first then only get the Branch table?
Thanks.
If you would like to obtain a collection of categories with service and branches you can eager load them in a single eloquent query.
$categories = Category::with('service.branches')->get();
But you still have to write a bit more if you would like to achieve your requirement.
Fractal Transformers might help you to do this. See their documentation here.
I am new to Laravel 5.4 and working on some query manipulation. Now I have created an query using query builder which is shown below:
$view = DB::table('blocks')
->leftjoin('programmes', 'blocks.programme_id', '=', 'programmes.id')
->select('blocks.id', 'blocks.programme_id', 'blocks.name', 'blocks.colour', 'blocks.year', 'programmes.title AS programme');
I have two more table "dates" and "modules". Each dates as well as module belongs to blocks.
Now I want to fetch all blocks with programmes, dates and modules. I know i can use with() method to get all of these. But as per my knowledge on Laravel, I can use with() method only if I have model file of each table and have relationship between them.
But do not want to use model and define relationship between them. I just want to know How can I get block data with programmes, dates and modules without creating model and defining relationship betwen them in model? Is there any other way to use with() method without model?
Block dates and modules are conditional, Sometime I dont want get data of this table with block.
Please help me on this.
You can't do it automatically. Eager loading is only for Eloquent model so you cannot use it with query builder. However in most cases you can use Eloquent also for getting more complicated queries (you can also use joins when using Eloquent) so you will be able to use eager loading.
But if you don't want to use Eloquent at all, obviously you will need to create some custom mechanism for eager loading.
I've just started using Laravel and I'm coming from a different system using an existing database. In this system there are 2 users table, one stock with the CMS and one custom one.
I want to create an Eloquent model which retrieves data from both tables into one model. I know I can use the following to create a relationship.
$this->hasOne('App\SecondUser', 'id', 'id);
But this results in 2 sql queries, and I want to join results from 2 tables before returning the model, in one join statement. How do I do this?
That might be a bit more complicated that you would expect.
First of all you have to use \DB facade to join the two collections(arrays) and then recreate the Eloquent collection from these arrays using Collection's make method.
More info about the Collection class here
An easier way might be to join them using standard laravel relationships and user something like Model::user->with('relation')->get.
But this will still create 2 queries (still relatively fast).
I am using this join in my code igniter model
$this->db->select('e.name, p.projects');
$this->db->from('example as e');
$this->db->join('procure as p', e.id = p.id');
$this->db->where('e.cityid', '1');
$this->db->where('e.status', '0');
I do not have separate table for join. Here is my data mapper, this is not giving any output.
I have two tables and I want to write a join query on them.I have this in my controller.
$example = new Example();
$example ->where_join_field('procure', FALSE);
Update
can you show me the snippet for joining three tables using data mapper.
Generally you don't do joins by hand with DMZ models (the sql generated will use joins nonetheless). The thing you are looking for is Relations.
You have to set up your model's relations, using the $has_one and $has_many attributes, keeping the naming conventions, creating the necessary tables for many-to-many and so on. You can read about these in the docs here and here.
Once you got your models set up, you can use the where_related and include_related methods where you have used joins before:
where_related is for when you want to filter the models you are querying on some related model's field values. So if you have a related project set up on your Example class, you can write ->where_related('project', 'procure', false); and it will filter the returned Example instances based on their related project's procedure field. So basically it's the same conditionals that you would put into the where SQL clause.
include_related is for when you want to include fields from related models or even whole instance. So if you write ->include_related('project', 'projects') when you query Example instances you will end up with a project_projects attribute on the returned instances. There are many options to control how these attributes should be created. Basically these are the fields you would have put into the select SQL clause.
There are magic methods created for every named relation and many other options, i refer you to the Get (Advanced) page of the documentation for start and free to explore the other pages describing relations.