Q:

How does Laravel generate SQL?

I'm brand new to Laravel and am working my way through the Laravel 6 from Scratch course over at Laracasts. The course is free but I can't afford a Laracasts membership so I can't ask questions there. 
I've finished Section 6 of the course, Controller Techniques, and am having unexpected problems trying to extend the work we've done so far to add a few new features. The course has students build pages that let a user show a list of articles, look at an individual article, create and save a new article, and update and save an existing article. The course work envisioned a very simple article containing just an ID (auto-incremented in the database and not visible to the web user), a title, an excerpt and a body and I got all of the features working for that. Now I'm trying to add two new fields: an author name and a path to a picture illustrating the article. I've updated the migration, rolled back and rerun the migration to include the new fields and got no errors from that. (I also ran a migrate:free and got no errors from that.) I've also updated the forms used to create and update the articles and added validations for the new fields. However, when I go to execute the revised create code, it fails because the SQL is wrong. 
The error message complains that the author field doesn't have a default, which is true, I didn't assign a default.  However, I did give it a value on the form. What perplexes me most is the SQL that it has generated: the column list doesn't show the two new columns. And that's not all: the values list is missing apostrophes around any of the string/text values. (All of the columns are defined as string or text.)
As I said, I'm completely new to Laravel so I don't know how to persuade Laravel to add the two new columns to the Insert statement nor how to make it put apostrophes around the strings in the values list. That hasn't come up in the course and I'm not sure if it will come up later. I was hoping someone could tell me how to fix this. All of my functionality was working fine before I added the  two new fields/columns.
Here is the error message: 
    SQLSTATE[HY000]: General error: 1364 Field 'author' doesn't have a default value (SQL: insert         into `articles` (`title`, `excerpt`, `body`, `updated_at`, `created_at`) values (Today in Canada, The ideal winter-beater, This car is the ideal winter-beater for the tough Canadian climate. It is designed to get you from A to B in style and without breaking the bank., 2020-02-15 17:37:54, 2020-02-15 17:37:54)) 

Here is ArticlesController: 
<?php

namespace App\Http\Controllers;

use App\Article;
use Illuminate\Http\Request;

class ArticlesController extends Controller
{
public function index()
{
    $articles = Article::latest()->get();
    return view ('articles.index', ['articles' => $articles]);
}

public function show(Article $article) 
{
    return view('articles.show', ['article' => $article]);
}

public function create() 
{
    return view('articles.create');
}

public function store() 
{
    //Stores a NEW article
    Article::create($this->validateArticle());
    return redirect('/articles');
}   

public function edit(Article $article) 
{
    return view('articles.edit', ['article' => $article]);
}

public function update(Article $article)
{
    //Updates an EXISTING article
    $article->update($this->validateArticle());
    return redirect('/articles/', $article->id);
}

public function validateArticle()
{
    return request()->validate([
        'title' => ['required', 'min:5', 'max:20'],
        'author' => ['required', 'min:5', 'max:30'],
        'photopath' => ['required', 'min:10', 'max:100'],
        'excerpt' => ['required', 'min:10', 'max:50'],
        'body' => ['required', 'min:50', 'max:500']
    ]);
}

public function destroy(Article $article)
{
    //Display existing record with "Are you sure you want to delete this? Delete|Cancel" option
    //If user chooses Delete, delete the record
    //If user chooses Cancel, return to the list of articles
}
}

Is there anything else you need to see?

A:

It may be possible because of you don't have defined that column in fillable property, to use mass assignment you have to specify that columns.
Try after adding that columns in fillable property.
Laravel mass assignment
Hope this helps :)

