How to Use Distinct In Relations Query In Laravel?

In Laravel, you can use the distinct method in a query for relations by chaining it onto the query builder instance. This method allows you to retrieve only unique results from a specific column in the related table.

For example, if you have a User model with a posts relationship that belongs to the Post model, you can use the distinct method to retrieve only unique posts for a specific user.

Here's an example query:

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$user = User::find(1);

$uniquePosts = $user->posts()->distinct()->get();

This will return a collection of unique posts associated with the user with an ID of 1. The distinct method ensures that only distinct rows are returned based on the specified column in the related table.

You can also pass a specific column to the distinct method to retrieve unique results based on that column. For example:

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$uniqueTitles = $user->posts()->distinct('title')->get();

This will return a collection of unique post titles for the user with an ID of 1.

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How to use distinct with where clause in Laravel for relations?

To use the distinct method with a where clause in Laravel for relations, you can chain the methods together in your query.

For example, if you have a Post model with a relation to a Category model and you want to retrieve the distinct categories of posts where the category name is "Technology", you can write the following query:

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$categories = Category::where('name', 'Technology')
    ->posts()
    ->select('category_id')
    ->distinct()
    ->get();

In this example, we are selecting only the category_id column from the posts table and applying the distinct method to get unique category IDs based on the where condition.

You can further customize your query by adding additional where conditions or including other relationships as needed.

How to use distinct in Laravel queries for polymorphic relationships?

To use the distinct method in Laravel queries for polymorphic relationships, you can do the following:

1. Define the polymorphic relationship in your models. For example, let's say you have a Post model and a Comment model that are both associated with a Like model using a polymorphic relationship.

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class Like extends Model
{
    public function likeable()
    {
        return $this->morphTo();
    }
}

class Post extends Model
{
    public function likes()
    {
        return $this->morphMany(Like::class, 'likeable');
    }
}

class Comment extends Model
{
    public function likes()
    {
        return $this->morphMany(Like::class, 'likeable');
    }
}

1. Now, if you want to retrieve all the likes for posts and comments, and apply the distinct method to get unique likes, you can use the following query:

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$likes = Like::query()
    ->where('created_at', '>=', now()->subDays(7))
    ->with(['likeable'])
    ->distinct()
    ->get();

This query will retrieve all the likes that were created in the last 7 days, along with their associated posts or comments, and apply the distinct method to ensure that only unique likes are returned.

1. You can also specify the columns you want to apply the distinct method on by passing them as arguments to the distinct method, like this:

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$likes = Like::query()
    ->select('user_id', 'likeable_type', 'likeable_id')
    ->where('created_at', '>=', now()->subDays(7))
    ->with(['likeable'])
    ->distinct('user_id', 'likeable_type', 'likeable_id')
    ->get();

This will apply the distinct method on the specified columns (user_id, likeable_type, and likeable_id), ensuring that only unique likes based on these columns are returned.

What is the performance impact of using distinct in Laravel relations query?

Using distinct in Laravel relations query can have a performance impact as it may involve additional processing to ensure the result set only includes unique values. This can lead to increased query execution time and possibly slower performance, especially when querying large datasets.

It is important to consider the trade-off between ensuring unique results and the potential performance impact when using distinct in Laravel relations query. It is recommended to carefully test and optimize queries to find a balance between accuracy and performance.