php - 一般错误 : 1215 Cannot add foreign key constraint

Question

我正在尝试从 products 表获取 price 值并将其设置为 sold 表。你能告诉我为什么会收到此错误吗？ product_id 和 user_id 工作正常。但是当我需要在 sold 表中创建外国 price 时，出现错误

已售表

    Schema::create('sold', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('user_id')->unsigned();
        $table->foreign('user_id')->references('id')->on('users');    
        $table->integer('product_id')->unsigned();  
        $table->foreign('product_id')->references('id')->on('products');
        $table->integer('price')->unsigned();
        $table->foreign('price')->references('price')->on('products');   
        $table->integer('bid_price')->unsigned();
        $table->foreign('bid_price')->references('bid_price')->on('products');     
        $table->timestamps();
    });

产品表

    Schema::create('products', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('user_id')->unsigned();
        $table->foreign('user_id')->references('id')->on('users');
        $table->string('slug');
        $table->string('title');
        $table->text('body');
        $table->integer('price');
        $table->integer('bid_price');
        $table->string('address');
        $table->string('condition');
        $table->integer('quantity');
        $table->string('img_1');
        $table->string('img_2');
        $table->string('img_3');
        $table->string('img_4');
        $table->integer('views');
        $table->timestamps();
    });

错误消息:

General error: 1215 Cannot add foreign key constraint (SQL
  : alter table `sold` add constraint sold_price_foreign foreign key (`price`
  ) references `products` (`price`))

编辑

`LATEST FOREIGN KEY ERROR
------------------------
2016-03-01 12:40:08 31a0 Error in foreign key constraint of table auction/#sql-2564_ef:
foreign key (`price`) references `products` (`price`):
Cannot find an index in the referenced table where the
referenced columns appear as the first columns, or column types
in the table and the referenced table do not match for constraint.
Note that the internal storage type of ENUM and SET changed in
tables created with >= InnoDB-4.1.12, and such columns in old tables
cannot be referenced by such columns in new tables.
See http://dev.mysql.com/doc/refman/5.6/en/innodb-foreign-key-constraints.html
for correct foreign key definition.`

Answer 1

Cannot find an index in the referenced table

您的产品表需要在您尝试引用的列上有一个索引。我想说这必须是唯一的，否则 MySQL 无法确定它引用的是哪一行。