Laravel改变外键约束

Question

我有一个表已创建的外键约束：

$table->foreign('cms_id')->references('id')->on('inventories'); 

我需要，使其在inventories表引用remote_id而不是id列改变这种外键。

我试图通过这样做：

public function up() 
    { 
     Schema::table('contents', function (Blueprint $table) { 
      $table->dropForeign('contents_cms_id_foreign'); 
      $table->foreign('cms_id')->references('remote_id')->on('inventories'); 
     }); 
    } 

但是，我得到：

[Illuminate\Database\QueryException]
SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL : alter table contents add constraint contents_cms_id_foreign foreign k ey (cms_id) references inventories (remote_id))

[PDOException]
SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint

Answer 1

两个步骤添加新的外键，除了分离到Schema::table：

public function up() 
{ 
    Schema::table('contents', function (Blueprint $table) { 
     $table->dropForeign('contents_cms_id_foreign'); 
     $table->integer('cmd_id')->unsigned(); 
    }); 

    Schema::table('contents', function (Blueprint $table) { 
     $table->foreign('cms_id')->references('remote_id')->on('inventories'); 
    }); 
}