更改列类型 Laravel 5

Change column type Laravel 5

为什么会出现以下错误

 SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'NOT NULL  
   COLLATE utf8mb4_unicode_ci' at line 1 (SQL: ALTER TABLE questions CHANGE category_id category_id INT DEFAULT  NOT NULL COLLATE utf8mb4_unicode_ci)

SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'NOT NULL  
   COLLATE utf8mb4_unicode_ci' at line 1 

通过执行以下代码:

Schema::table('questions', function(Blueprint $table) {
     $table->integer('category_id')->unsigned()->change();
});

改用unsignedInteger

Schema::table('questions', function(Blueprint $table) {
   $table->unsignedInteger('category_id')->change();
});