How to Fix the \"Cannot Delete or Update a Parent Row\" Error in Laravel?

Resolving "Cannot Delete or Update a Parent Row" Error in Laravel

When deleting a post that has associated likes, you encounter the following error:

SQLSTATE[23000]: Integrity constraint violation: 1451 Cannot delete or update a parent row: a foreign key constraint fails

This error suggests a schema issue related to foreign key constraints.

Problem Analysis

The likes table has a foreign key constraint on post_id that references the id column in the posts table. When you attempt to delete a post without first deleting its associated likes, the foreign key constraint on likes.post_id prevents the operation.

Solution 1: Using onDelete('cascade')

To resolve the issue, you can configure the onDelete action for the likes.post_id foreign key in the likes migration file:

<code class="php">Schema::create('likes', function (Blueprint $table) {
    $table->integer('post_id')->unsigned();
    $table->foreign('post_id')->references('id')->on('posts')->onDelete('cascade');
});</code>

With this configuration, when a post is deleted, all associated likes will be automatically deleted, resolving the foreign key violation.

Solution 2: Explicitly Deleting Likes

Alternatively, you can explicitly delete the likes associated with the post before deleting the post itself. This approach requires adding the following lines to your PostController.php:

<code class="php">$post->likes()->delete();
$post->delete();</code>

Relationship-Based Solution

If your models have a relationship configured between them, you can use the following approach to delete both the post and its associated likes in a single operation:

<code class="php">$post->likes()->delete();
$post->delete();</code>

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