mysql - 在 Laravel 中删除外键

Question

我正在尝试使用迁移删除外键。

这是我的代码

public function up()
    {
        Schema::table('tbl_social_media_links', function (Blueprint $table) {
            $table->renameColumn('vchr_link', 'vchr_social_media_link');
            $table->dropColumn('vchr_social_media_name');
            $table->integer('fk_int_business_id')->unsigned()->after('pk_int_sm_id');
            $table->foreign('fk_int_business_id')->references('pk_int_business_id')
                ->on('tbl_business_details')->onDelete('cascade');
            $table->integer('int_social_media_type')->after('fk_int_business_id');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('tbl_social_media_links', function (Blueprint $table) {
            Schema::disableForeignKeyConstraints();
            $table->string('vchr_social_media_name')->after('pk_int_sm_id');
            $table->dropColumn('fk_int_business_id');
            $table->dropColumn('int_social_media_type');
            $table->renameColumn('vchr_social_media_link', 'vchr_link');
            Schema::enableForeignKeyConstraints();
        });
    }

也尝试过 $table->dropForiegn('fk_int_business_id');

我不断收到类似错误

General error: 1553 Cannot drop index 'tbl_social_media_links_fk_int_business_id_foreign': needed in a foreign key constraint (
  SQL: alter table `tbl_social_media_links` drop `fk_int_business_id`)

有人可以帮我让它工作吗？

我什至尝试使用 sql 删除它，但它说 无法删除“fk_int_business_id”；检查列/键是否存在

Answer 1

这就是我要做的:

/**
 * Run the migrations.
 *
 * @return void
 */
public function up()
{
    Schema::table('tbl_social_media_links', function (Blueprint $table) {
        $table->foreign('fk_int_business_id')
            ->references('pk_int_business_id')
            ->on('tbl_business_details')
            ->onDelete('cascade');;
    });
}

/**
 * Reverse the migrations.
 *
 * @return void
 */
public function down()
{
    Schema::table('tbl_social_media_links', function (Blueprint $table) {
        $table->dropForeign(['fk_int_business_id']);
    });
}

请注意，我在 dropForeign 中使用字符串数组作为参数而不是字符串进行发送，因为行为不同。对于数组，您可以使用列名称，但对于字符串，您需要使用键名称。

但是，我发现，即使删除外键，索引键仍然存在，所以这可以解决这个问题:

/**
 * Run the migrations.
 *
 * @return void
 */
public function up()
{
    Schema::table('tbl_social_media_links', function (Blueprint $table) {
        $table->foreign('fk_int_business_id')
            ->references('pk_int_business_id')
            ->on('tbl_business_details')
            ->onDelete('cascade');;
    });
}

/**
 * Reverse the migrations.
 *
 * @return void
 */
public function down()
{
    Schema::table('tbl_social_media_links', function (Blueprint $table) {
        $index = strtolower('tbl_social_media_links'.'_'.implode('_', ['fk_int_business_id']).'_foreign');
        $index = str_replace(['-', '.'], '_', $index);

        $table->dropForeign($index);
        $table->dropIndex($index);
    });
}

另请注意，在本例中，我生成键名称而不是使用数组，因为我找不到任何其他方法来仅使用列名称删除索引键。

另一方面，请注意您可能需要拆分语句才能删除该列:

/**
 * Reverse the migrations.
 *
 * @return void
 */
public function down()
{
    Schema::table('tbl_social_media_links', function (Blueprint $table) {
        $index = strtolower('tbl_social_media_links'.'_'.implode('_', ['fk_int_business_id']).'_foreign');
        $index = str_replace(['-', '.'], '_', $index);

        $table->dropForeign($index);
        $table->dropIndex($index);
    });

    Schema::table('tbl_social_media_links', function (Blueprint $table) {
        $table->dropColumn('fk_int_business_id');
    });
}