I am new to laravel and confused about some query methods.
find($id) is useful and returns a nice array, but sometimes I need to select by other fields rather than id.
The Laravel document said I could use where('field', '=', 'value') and return a bunch of data, which is fine.
What I can't understand is why I need to add ->first() every time, even if I am pretty sure there is only one single row matches the query.
It goes like this:
$query->where(..)->orderBy(..)->limit(..) etc.
// you can chain the methods as you like, and finally you need one of:
->get($columns); // returns Eloquent Collection of Models or array of stdObjects
->first($columns); // returns single row (Eloquent Model or stdClass)
->find($id); // returns single row (Eloquent Model or stdClass)
->find($ids); // returns Eloquent Collection
// those are examples, there are many more like firstOrFail, findMany etc, check the api
$columns is an array of fields to retrieve, default array('*')
$id is a single primary key value
$ids is an array of PKs, this works in find method only for Eloquent Builder
// or aggregate functions:
->count()
->avg()
->aggregate()
// just examples here too
So the method depends on what you want to retrieve (array/collection or single object)
Also the return objects depend on the builder you are using (Eloquent Builder or Query Builder):
User::get(); // Eloquent Colleciton
DB::table('users')->get(); // array of stdObjects
even if I am pretty sure there is only one single row matches the query.
Well Laravel cant read your mind - so you need to tell it what you want to do.
You can do either
User::where('field', '=', 'value')->get()
Which will return all objects that match that search. Sometimes it might be one, but sometimes it might be 2 or 3...
If you are sure there is only one (or you only want the first) you can do
User::where('field', '=', 'value')->first()
get() returns an array of objects (multiple rows)
while
first() returns a single object (a row)
You can of course use get() when you know it will return only one row, but you need to keep that in mind when addressing the result:
using get()
$rez = \DB::table('table')->where('sec_id','=','5')->get();
//will return one row in an array with one item, but will be addressed as:
$myfieldvalue = $rez[0]->fieldname;
using first()
$rez = \DB::table('table')->where('sec_id','=','5')->first();
// will also return one row but without the array, so
$myfieldvalue = $rez->fieldname;
So it depends on how you want to access the result of the query: as an object or as an array, and also depends on what "you know" the query will return.
first() is the equivalent of LIMIT 1 at the end of your SELECT statement. Even if your query would return multiple rows, if you use first() it will only return the first row
Related
My concern is that while orderBy is applied to the query, I'm not sure how the sortBy is applied?
The reason for using sortBy in my case is because I get the collection via the model (i.e. $user->houses->sortBy('created_at')).
I'm just concerned about the performance: is sortBy simply looping each object and sorting them?, or is Laravel smart enough to simply transform the sortBy into an orderBy executed within the original query?
You need orderBy in order to perform a SQL order.
$user->houses()->orderBy('created_at')->get()
You can also eager load the houses in the right order to avoid N+1 queries.
$users = User::with(['houses' => function ($query) {
return $query->orderBy('created_at');
}])->get();
$orderedHouses = $users->first()->houses;
The sortBy method is applied to the Collection so indeed, it will looping each objects.
The orderBy() method is much more efficient than the sortBy() method when querying databases of a non-trivial size / at least 1000+ rows. This is because the orderBy() method is essentially planning out an SQL query that has not yet run whereas the sortBy() method will sort the result of a query.
For reference, it is important to understand the difference between a Collection object and a Builder object in Laravel.
A builder object is, essentially, an SQL query that has not been run. In contrast, a collection is essentially an array with some extra functionality/methods added. Sorting an array is much less efficient than pulling the data from the DB in the correct format on the actual query.
example code :
<?php
// Plan out a query to retrieve the posts alphabetized Z-A
// This is still a query and has not actually run
$posts = Posts::select('id', 'created_at', 'title')->orderBy('title', 'desc');
// Now the query has actually run. $posts is now a collection.
$posts = $posts->get();
// If you want to then sort this collection object to be ordered by the created_at
timestamp, you *could* do this.
// This will run quickly with a small number or rows in the result,
// but will be essentially unusable/so slow that your server will throw 500 errors
// if the collection contains hundreds or thousands or objects.
$posts = $posts->sortBy('created_at');
This eloquent collection provides this result:
$id = Model::where('s_id', $s_id)->pluck('l_id');
print_r($id)
Illuminate\Support\Collection Object
(
[items:protected] => Array
(
[0] => 31242682774
)
)
How do I return only the "31242682774" value as a string and not a collection?
EDIT ANSWER:
All I had to do is:
$id = Model::where('s_id', $s_id)->pluck('l_id')->first();
Any better options?
If you only need a single value, not multiple values, pluck isn't what you want. There is a method called value on Query Builder that returns a single value:
Model::where('s_id', $s_id)->value('l_id');
Laravel 6.x Docs - Query Builder - Retrieving Results - Retrieving A Single Row / Column From A Table value
It compares to when it the process you wanna do it. On the query execution or after. The most common approach would probably be.
$id = Model::where('s_id', $s_id)->first()->l_id;
This will execute after, meaning the query builder will fetch all columns in the row. In general in Laravel you don't that often work with strings and or other abstractions than your model. Model::where('s_id', $s_id)->first() will return your model and select the l_id property on it.
The approach you chosen is the database way, you only select the l_id and return it as a collection and select the first item from there. This is thou a very performance efficient way of doing it since the database does all the work and is very quick at it.
$id = Model::where('s_id', $s_id)->pluck('l_id')->first();
The reason why it is a collection, it is mainly made for selecting multiple id's, so if you query returned multiple rows multiple ids would be returned. Here you can see an example of pluck in conditional queries, where it is most often used.
$teamIds = Team::where('type', 'admin')->pluck('id');
$adminUsers = User::where('team_id', $teamIds)->get();
Your solution is perfect for what you need, just trying to bring clarity on why and a example of how it is often used.
I'm a bit new to this, and was originally trying to check if my model was returning results with isEmpty(), but thought I'd try count() instead, then I came across the following:
I've got the following code, which returns data from my model:
$results = Game::where('code', '=', $code)->with('genre', 'creator')
And whether I use first() or get() combined with count(result) or $results->count() I get different values, and I'm not sure why.
when using ->first()
dd($results->count()) = 11930 // Number of rows in the db
when using ->get()
dd($results->count()) = 1 // What I'd expect the query to return
when using ->first()
dd(count($results)) = "count(): Parameter must be an array or an object that implements Countable"
when using ->get()
dd(count($results)) = 1
I don't understand 1) why when using first, the count is the same as every row in the db. 2) Why count() can't be used with first().
Is anyone able to shed some light as to why I can't use count on first as I'd like to?
Update:
I'm also not able to use ->isEmpty() with ->first() but can with ->get()...?
When I try using it with first, I get Illuminate\Database\Query\Builder::isEmpty does not exist.
Disclaimer: I'm not sure why your database count and your results count aren't the same, however I can shed some light on the different types of count.
Game::where('code', '=', $code)->count();
This is being called on a query builder instance. It is run on the database query, without selecting all the rows. Check out the title Aggregates here: https://laravel.com/docs/5.7/queries
Game::where('code', '=', $code)->get()->count();
As soon as your use get() laravel selects the rows, boots them all as models, and creates a collection. This count is on the collection (a bit like an array) so just gets the number that are returned (i.e. if they are paginated or anything like that it will just get that amount). Check out Count here.
Game::where('code', '=', $code)->first()->count();
This is being run on the first returned model... unless you've written it, a default laravel model won't have a count() method.
count($results)
Finally, count() when not a class method is just the default php function that returns the length of an array or other object (documentation).
First of all,
get() returns collection of objects while first() returns modal object of query.
$results = Game::where('code', '=', $code)->with('genre', 'creator')
dd($results->count()) = 11930 // Number of rows in the db
when using ->get()
$results = Game::where('code', '=', $code)->with('genre', 'creator')->get()
dd($results->count()) = 1
because it has collection, which contains numbers of objects of database data. As ->count getting only one collection so it returns 1.
I am trying to get the value of a single column using Eloquent:
MyModel::where('field', 'foo')->get(['id']); // returns [{"id":1}]
MyModel::where('field', 'foo')->select('id')->first() // returns {"id":1}
However, I am getting anything but the value 1. How can get that 1?
NOTE: It is possible that the record with field of foo does not exist in the table!
EDIT
I am ideally looking for a single statement that either returns the value (e.g. 1) or fails with a '' or null or other. To give you some more context, this is actually used in Validator::make in one of the rules:
'input' => 'exists:table,some_field,id,' . my_query_above...
EDIT 2
Using Adiasz's answer, I found that MyModel::where('field', 'foo')->value('id') does exactly what I need: returns an integer value or an empty string (when failed).
Laravel is intuitive framework... if you want value just call value() method.
MyModel::find(PK)->value('id');
MyModel::where('field', 'foo')->first()->value('id');
You're using the Eloquent query builder, so by default, it'll return an Eloquent model with only the value you wish.
The method you're looking for is pluck() which exists in the normal query builder (of which the Eloquent one extends) so your code should look as follows:
MyModel::where('field', 'foo')->pluck('id'); // returns [1]
The value() method that is being used in the other answers is an Eloquent model method. Using that means that the framework queries the database, hydrates the model and then returns only that value. You can save yourself a few keystrokes and few CPU cycles by using pluck() and have it handled simply in one query.
I'm confused as to when ->get() in Laravel...
E.G. DB::table('users')->find(1) doesn't need ->get() to retrieve the results, neither does User::find(1)
The laravel docs say "...execute the query using the get or first method..."
I've read the Fluent Query Builder and Eloquent docs but don't understand when the usage of get() is required...
Thanks for the help
Since the find() function will always use the primary key for the table, the need for get() is not necessary. Because you can't narrow your selection down and that's why it will always just try to get that record and return it.
But when you're using the Fluent Query Builder you can nest conditions as such:
$userQuery = DB::table('users');
$userQuery->where('email', '=', 'foo#bar.com');
$userQuery->or_where('email', '=', 'bar#foo.com');
This allows you to add conditions throughout your code until you actually want to fetch them, and then you would call the get() function.
// Done with building the query
$users = $userQuery->get();
For find(n), you retrieve a row based on the primary key which is 'n'.
For first(), you retrieve the first row among all rows that fit the where clauses.
For get(), you retrieve all the rows that fit the where clauses. (Please note that loops are required to access all the rows or you will get some errors).
find returns one row from the database and represent it as a fluent / eloquent object. e.g. SELECT * FROM users WHERE id = 3 is equivalent to DB::table('users')->find(3);
get returns an array of objects. e.g. SELECT * FROM users WHERE created_at > '2014-10-12' is equivalent to DB::table('users')->where('created_at', '>', '2014-10-12')->get() will return an array of objects containing users where the created at field is newer than 4014-10-12.
The get() method will give you all the values from the database that meet your parameters where as first() gets you just the first result. You use find() and findOrFail() when you are searching for a key. This is how I use them:
When I want all data from a table I use the all() method
Model::all();
When I want to find by the primary key:
Model::find(1)->first();
Or
Model::findOrFail(1)->first();
This will work if there is a row with a primary key of one. It should only retrieve one row so I use first() instead of get(). Remember if you deleted the row that used key 1, or don't have data in your table, your find(1) will fail.
When I am looking for specific data as in a where clause:
Model::where('field', '=', 'value')->get();
When I want only the first value of the data in the where clause.
Model::where('field', '=', 'value')->first();
Basically what you need to understand is that get() return a collection(note that one object can be in the collection but it still a collection) why first() returns the first object from the result of the query(that is it returns an object)
#Take_away
Get() return a collection first() return an object
You can use get() method with latest() method to get the latest record that were recently added to your table
For example
$user=Student::latest()->get();
return all the data in descending order