I want to know the difference between laravel eloquent conisgnment->runsheet->name and $consignment->runsheet()->name
i notice that there is performance difference but why? also I notice that when I try to get relationship property like $consignment->runsheet->name it work fine but $consignment->runsheet()->name doesn't work
The first one
$consignment->runsheet
retrieve a collection (so it's already made a query to DB)
while the second
$consignment->runsheet()
is a query builder (hasn't made a database query) you can chain it like any query builder instance
so if you want to get a property from the second one you can do it like:
$consignment->runsheet()->first()->name;
OR
$consignment->runsheet()->value('name');
Related
When I use:
$myModel::find(1);
I'm completely fine using accessors, for example - that's because it returns an instance of the model?
And if I use
$myModel::where('foo', 'bar');
I can no longer access any accessors or model function, or even relationships on myModel Is that expected behavior and if it is - how should I execute a where query so I can keep using the model's relations?
you need to fetch the model.After that everything will work fine.
$myModel::where('foo', 'bar')->firstOrFail();
In backend I have a list of records. And this list displays all records of this type. It is possible to override this query?
In controller I have Eloquent query and i grab some data from database,
and i set this data in $query_data variable. Howe push this data in list view?
unfortunately, I didn't get exactly your point of telling override query, if you mean that set some condition in fetching data from database in Eloquent you have to use where for example in the example below we have users which their gender is male:
$users=User::where('gender','male')->get();
for set more condition you can do like this:
$users=User::where([['gender','male'],['status',1]])->get();
and for showing the variable in your view you can use compact method:
return view('YOUR BLADE FILE NAME',compact('users'));
hope be helpful bro
I would like to understand what happen when using the toArray () method in a case like this:
Ad::query()->with('nominations')->where(['id'=>$id])->get()->toArray();
Eloquent prevents the construction of the collection and the hydration of individual model objects and directly returns an array or eloquent first hydrates the collection and the model objects and then converts everything into an array (thus doing an extra operation)?
If the answer was the second, how can I get the first behavior with eloquent?
I specify with eloquent because it would be nice to be able to do this by continuing to refer in an abstract way to the entities without then mentioning specific database features in the code (for example the name of the tables).
Answering both your questions. The second one will happen. And you can't make Eloquent create an array, you can just convert an object or collection to an array.
Also, your query has a lot of redundant code, you could just do this:
Ad::with('nominations')->find($id)->toArray()
I use Entity Framework in combination with an Oracle database. If I create a query like
myLinqStatement.ToListAsync()
I get wrong data returned as a result. If I change the statement to
myLinqStatement.AsNoTracking.ToListAsync()
I get the correct data.
I also checked the native SQL query, which is generated by myLinqStatement.ToListAsync(). The generated SQL query is correct, because I get the correct data.
So is there a problem in the mapping? And why is it working with AsNoTracking?
Thanks!
What AsNoTracking does is to retrieve the data without attaching it to the context, hence any changes you apply over the data do not take effect unless you attach it again so that EF knows it should track its changes.
The code snippets you've provided do not show the whole picture, from the moment a context is created, but is it possible that other parts of your code mutate data before you call myLinqStatement.ToListAsync()?
As you mention that myLinqStatement.AsNoTracking.ToListAsync() returns expected data, makes me assume that there are some side effects in your code that AsNoTracking simply is not aware so just returns whatever it finds in your db
I came across this question because I had a similar issue with Entity Framework Core querying a DB view, the issue was cause because view didn't have a key defined, after defining a key for the entity that map to that DB view, the query returned the same result in both cases (using AsNoTracking or without using it).
In T-SQL a key for a DB view can be defined this way:
CREATE UNIQUE CLUSTERED INDEX UQ_MyDBViewName_ColumnKey
ON dbo.MyDBViewName (ColumnKey);
And in code, you can map the key using the [Key] attribute in the corresponding property of the entity or using the EF fluent API. It will depend of what the project is using.
Either way, using AsNoTracking on a query that goes directly to a DB view makes a lot of sense. Also, if for some reason the query of the view does not allow us to define a key for that view, then the option is to use AsNoTracking.
Hope it helps anyone else having the same issue.
I have Question and Answer models. The Question hasMany Answers. Following commands run in the php artisan tinker mode invoke a database query for no apparent reason:
$q = new Question;
$q->answers[] = new Answer; // invokes the below query
// the executed query
select * from `answers` where `answers`.`question_id` is null and `answers`.`question_id` is not null
As you see, there is no need for database call whatsoever. How can I prevent it?
When you do $q->answers, Laravel tries to load all of the answers on the question object - regardless of whether they exist or not.
Any time you access a relationship on a model instance, you can either call it like answers() and get a query builder back, or you can call it like answers without parentheses and Laravel will fetch a collection for you based on the relationship.
You can prevent it easily by doing this:
$q = new Question;
$a = new Answer;
And then, when you're ready to save them, associate them with each other. In its simplest form, that looks like this:
$q->save();
$q->answers()->save($answer);
It's doing that because you're assigning it to the Question object. It wants to see if you're adding an extant record reference. All Laravel Eloquent models contain magic methods for properties, and trying to use them as temporary data storage is a really bad idea unless you've defined a property on them ahead of time for that specific purpose.
Just use a regular array instead and then associate them after the models have been prepared.
Documentation on one-to-many relationships:
https://laravel.com/docs/5.1/eloquent-relationships#one-to-many