database/migrations/2024_05_07_123620_create_lessons_table.php

@@ -15,7 +15,10 @@ return new class extends Migration
             $table->id();
             $table->string('name');
             $table->string('type');
-            $table->date('lesson_date')->nullable();
+            $table->date('lesson_date');
+            $table->foreignId('grade_id')->constrained('grades')->onDelete('cascade');
+            $table->foreignId('subject_id')->constrained('subjects')->onDelete('cascade');
+            $table->foreignId('teacher_id')->constrained('teachers')->onDelete('cascade');
             $table->timestamps();
         });
     }

database/migrations/2024_05_07_125455_add_foreign_key_to_student_subject.php

@@ -12,7 +12,7 @@ return new class extends Migration
     public function up(): void
     {
         Schema::table('student_subject', function (Blueprint $table) {
-            $table->foreignId('lesson_id')->constrained('lessons')->onDelete('cascade');
+            $table->foreignId('lesson_id')->nullable()->constrained('lessons')->onDelete('cascade');
         });
     }