QueryException (23000) SQLSTATE[23000]: Integrity constraint v1452 - mysql

Question

I am sucked by this error since this week could any one help me please !
SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (practice2.posts, CONSTRAINT posts_category_id_foreign FOREIGN KEY (category_id) REFERENCES categories (id)) (SQL: insert into posts (author_id, updated_at, created_at) values (2, 2017-11-13 05:48:53, 2017-11-13 05:48:53))
my codes are:
Blog controller :
public function store(Requests\PostRequest $request)
{
$request->user()->posts()->create($request->all());
redirect('/backend/blog')->with('message', 'Your post was created successfully!');
}
**migration:**
public function up()
{
Schema::create('posts', function (Blueprint $table) {
$table->increments('id');
$table->integer('author_id')->unsigned();
$table->foreign('author_id')->references('id')->on('users')->onDelete('restrict');
$table->string('tittle');
$table->string('slug')->unique;
$table->text('excerpt');
$table->text('body');
$table->string('image')-> nullable();
$table->timestamps();
});
}
alter_post_migration :
public function up()
{
Schema::table('posts', function (Blueprint $table) {
$table->integer('category_id')->unsigned();
$table->foreign('category_id')->references('id')->on('categories')->onDelete('restrict');
//
});
}
create post form:
<div class="box-body ">
{!! Form::model($post, [
'method' => 'POST',
'route' => 'back.store'
]) !!}
<div class="form-group {{ $errors->has('tittle') ? 'has-error' : '' }}">
{!! Form::label('tittle') !!}
{!! Form::text('tittle', null, ['class' => 'form-control']) !!}
#if($errors->has('tittle'))
<span class="help-block">{{ $errors->first('tittle') }}</span>
#endif
</div>
<div class="form-group {{ $errors->has('slug') ? 'has-error' : '' }}">
{!! Form::label('slug') !!}
{!! Form::text('slug', null, ['class' => 'form-control']) !!}
#if($errors->has('slug'))
<span class="help-block">{{ $errors->first('slug') }}</span>
#endif
</div>
<div class="form-group">
{!! Form::label('excerpt') !!}
{!! Form::textarea('excerpt', null, ['class' => 'form-control']) !!}
</div>
<div class="form-group {{ $errors->has('body') ? 'has-error' : '' }}">
{!! Form::label('body') !!}
{!! Form::textarea('body', null, ['class' => 'form-control']) !!}
#if($errors->has('body'))
<span class="help-block">{{ $errors->first('body') }}</span>
#endif
</div>
<div class="form-group {{ $errors->has('published_at') ? 'has-error' : '' }}">
{!! Form::label('published_at', 'Publish Date') !!}
{!! Form::text('published_at', null, ['class' => 'form-control', 'placeholder' => 'Y-m-d H:i:s']) !!}
#if($errors->has('published_at'))
<span class="help-block">{{ $errors->first('published_at') }}</span>
#endif
</div>
<div class="form-group {{ $errors->has('category_id') ? 'has-error' : '' }}">
{!! Form::label('category_id', 'Category') !!}
{!! Form::select('category_id', App\Category::pluck('tittle', 'id'), null, ['class' => 'form-control', 'placeholder' => 'Choose category']) !!}
#if($errors->has('category_id'))
<span class="help-block">{{ $errors->first('category_id') }}</span>
#endif
</div>
<hr>
{!! Form::submit('Create new post', ['class' => 'btn btn-primary']) !!}
{!! Form::close() !!}
</div>

Answer 1

The error:
Integrity constraint violation: 1452 Cannot add or update a child row:
a foreign key constraint fails (practice2.posts, CONSTRAINT
posts_category_id_foreign FOREIGN KEY (category_id) REFERENCES
categories (id))
comes when two table share a relationship of foreign key and you are trying to add some data in child table and its associated record does not exist in the parent table. So check the data accordingly and try again.