Im trying to select only specific attributes on the many-to-many relation users, just like in one-to-one. But using select() on belongsToMany() seem to be ignored and i'm still getting all the User attributes.
class Computer extends Eloquent {
public function users() {
return $this->belongsToMany("User")->select("email");
}
public function admin() {
return $this->hasOne("User")->select("email");
}
}
Computer::with("users")->get();
Is there a way of filtering only specified columns from related entity with belongsToMany()?
Yes, you actually can.
Computer::with("users")->get(array('column_name1','column_name2',...));
Be careful though if you have the same column name for both tables linked by your pivot table. In this case, you need to specify the table name in dot notation, tableName.columnName. For example if both users and computer has a column name id, you need to do :
Computer::with("users")->get(array('users.id','column_name2',...));
According to Taylor Otwell it is not currently possible: https://github.com/laravel/laravel/issues/2679
I have tried to use a lists('user.email') at the end of the query but I can't make it work.
Computer::with(["users" => function($query){
$query->select('column1','column2','...');
}])->get();
Related
I am a newbie to Laravel 5.2 and am working on a legacy system and am a bit confused regarding eloquent and would appreciate someone giving me the code.
There are 3 tables:
cards
categories
cards2cat
cards can be part many categories which are kept in cards2cat table.
The cards2cat table has the following structure
id (primary key)
image (card)
category
What I want to do is to have a method in the Cards model called something like getCardsWithCategores which returned the cards info plus the names of the categories from the category table.
The categories table has a key of id and a field category.
Thanks!
Go to your Card2Cats model and add this:
public function categories()
{
return $this->hasOne('App\Categories','id','category');
}
public function cards()
{
return $this->hasOne('App\Cards','id','image');
}
For the query you do this:
$cards = Card2Cat::with('categories','cards')->get();
foreach ($cards as $key => $value) {
echo $value->id.', Card:'.$value->cards->name.', Category:'.$value->categories->category.'<br>';
//$value->cards gives you all column of cards and you can do
//$value->cards->colName
// same goes for $value->categories
}
Make sure the spelling of your classes and table column names are correct before running the code :D
public IQueryable<Student> GetStudents()
{
var balance = (from StandardX in db.Standards
join StudentX in db.Students
on StandardX.StandardId equals StudentX.StandardRefId
select new { StudentX.StudentID, StudentX.StudentName, StandardX.StandardName });
return balance; // I can't handle that. how can I return? Please help.
}
Question:
I have two tables named respectively standard and student. I want to retrieve all student information via foreign key relationship. I searched everywhere regarding this topic but didn't find any suitable solution. Please help me with solving this issue.
If you have the relationship configured, try the include statement (assuming standard is the parent and 1:1, otherwise flip and/or add collection):
var balance = (from StandardX std in db.Standards.Include("Student")
select new { std.Student.StudentID, std.Student.StudentName, std.StandardName });
https://msdn.microsoft.com/en-us/library/bb896272.aspx
Suppose I have a class Parent, with two subclasses, AChild and BChild. I have these mapped to a single table using Entity Framework 5.0.0 on .NET 4.5, using TPH.
public abstract class Parent {
public string Type { get; set; } // Column with this name in DB is discriminator.
public string Status { get; set; }
}
public class AChild : Parent {
// Other stuff.
}
public class BChild : Parent {
// Other stuff.
}
The code to configure the mapping:
class ParentConfiguration : EntityTypeConfiguration<Parent> {
Map((EntityMappingConfiguration<AChild> mapping) => mapping
.Requires("Type")
.HasValue("A"));
Map((EntityMappingConfiguration<BChild> mapping) => mapping
.Requires("Type")
.HasValue("B"));
}
I have a need to run a query that returns both AChild and BChild objects. However, it needs to filter ONLY the AChild rows by a second column, which in this example I will call Status.
Ideally I would want to do the following:
public IList<Parent> RunQuery() {
IQueryable<Parent> query =
this.context.Set<Parent>()
.Where((Parent parent) => !parent.Type.Equals("A") || parent.Status.Equals("Foo"))
.OrderBy((Parent parent) => parent.Number);
return query.ToList();
}
This doesn't work. It insisted on looking for a "Type1" column instead of just letting both the discriminator and a "Type" property be mapped to the same "Type" column.
I know of the "OfType" extension method that can be used to completely filter down to one type, but that's too broad a brush in this case.
I could possibly run multiple queries and combine the results, but the actual system I'm building is doing paging, so if I need to pull back 10 rows, it gets messy (and inefficient) to query since I'll either end up pulling back too many rows, or not pull back enough and have to run extra queries.
Does anyone have any other thoughts?
There are few problems. First of all you cannot have discriminator mapped as a property. That is the reason why it is looking for Type1 column - your Type property results in second column because the first one is already mapped to .NET types of your classes. The only way to filter derived types is through OfType.
The query you want to build will be probably quite complex because you need to query for all Bs and concatenate them with result of query for filtered As. It will most probably not allow you to concatenate instances of Bs with As so you will have to convert them back to parent type.
I'm trying to use the CodeFirst data migrations in EF5 with a table that has a composite natural key. Is it possible to specify this in the first argument to DbSet.AddOrUpdate, like
context.Table1.AddOrUpdate(
t=>t.Column1 && t.Column2,
new Table1 { properties... }
);
How would one specify using more than one property in this case?
Thanks,
Matthew
Turns out I had to use an anonymous type in the first argument, e.g.
t => new { t.Column1, t.Column2 }
I implemented inheritance with a discriminator field so all my records are in the same table. My basetype is Person (also the name of the table) and Driver and Passenger inherit from it. I receive instances of the correct type (Driver and Passenger) when I perform a query on the object context to Person. example:
var q = from d in ctx.Person
select d;
But I also create a function that calls a stored procedure and mapped the output of the function to the type Person. But now I get a list of Person and not Drivers or Passengers when I execute this method.
Anybody an idea how to solve this or is this a bug in EF4?
AFAIK, you can't use discriminator mapping (e.g TPH) when dealing with stored procedure mappings.
The stored procedure must be mapped to a complex type or custom entity (e.g POCO), the mapping cannot be conditional.
What you could do is map it to a regular POCO, but then project that result set into the relevant derived type (manual discrimination).
E.g:
public ICollection<Person> GetPeople()
{
var results = ExecuteFunction<Person>(); // result is ObjectResult<Person>
ICollection<Person> people = new List<Person>();
foreach (var result in results)
{
if (result.FieldWhichIsYourDiscriminator == discriminatorForDriver)
{
people.Add((Driver)result);
}
// other discriminators
}
}
If your always expecting a collection of one type (e.g only Drivers), then you wouldn't need the foreach loop, you could just add the range. The above is in case you are expecting a mixed bag of different people types.
Would be interested to see other answers, and if there is a better way though - but the above should work.