Question

我正在做一个学校项目，需要使用lard和erd来建立我的数据库。我正在尝试使用外键进行迁移。

如何在Laravel中使用外键？

这是我的桌子：

\\\\\\\\

        C:\xampp\htdocs\newapps>php artisan migrate:fresh -v
        Dropped all tables successfully.
        Migration table created successfully.
Migrating: 2014_10_12_000000_create_users_table
Migrated:  2014_10_12_000000_create_users_table
Migrating: 2014_10_12_100000_create_password_resets_table
Migrated:  2014_10_12_100000_create_password_resets_table
Migrating: 2019_01_13_151934_create_customer_orders_table

   Illuminate\Database\QueryException  : SQLSTATE[42000]: Syntax error or access violation: 1072 Key column 'customer_id' doesn't exist in table (SQL: alter table `customer_orders` add constraint `customer_orders_customer_id_foreign` foreign key (`customer_id`) references `customers` (`customer_id`))

  at C:\xampp\htdocs\newapps\vendor\laravel\framework\src\Illuminate\Database\Connection.php:664
    660|         // If an exception occurs when attempting to run a query, we'll format the error
    661|         // message to include the bindings with SQL, which will make this exception a
    662|         // lot more helpful to the developer instead of just the database's errors.
    663|         catch (Exception $e) {
  > 664|             throw new QueryException(
    665|                 $query, $this->prepareBindings($bindings), $e
    666|             );
    667|         }
    668|

  Exception trace:

  1   PDOException::("SQLSTATE[42000]: Syntax error or access violation: 1072 Key column 'customer_id' doesn't exist in table")
      C:\xampp\htdocs\newapps\vendor\laravel\framework\src\Illuminate\Database\Connection.php:458

  2   PDOStatement::execute()
      C:\xampp\htdocs\newapps\vendor\laravel\framework\src\Illuminate\Database\Connection.php:458

  3   Illuminate\Database\Connection::Illuminate\Database\{closure}("alter table `customer_orders` add constraint `customer_orders_customer_id_foreign` foreign key (`customer_id`) references `customers` (`customer_id`)", [])
      C:\xampp\htdocs\newapps\vendor\laravel\framework\src\Illuminate\Database\Connection.php:657

  4   Illuminate\Database\Connection::runQueryCallback("alter table `customer_orders` add constraint `customer_orders_customer_id_foreign` foreign key (`customer_id`) references `customers` (`customer_id`)", [], Object(Closure))
      C:\xampp\htdocs\newapps\vendor\laravel\framework\src\Illuminate\Database\Connection.php:624

  5   Illuminate\Database\Connection::run("alter table `customer_orders` add constraint `customer_orders_customer_id_foreign` foreign key (`customer_id`) references `customers` (`customer_id`)", [], Object(Closure))
      C:\xampp\htdocs\newapps\vendor\laravel\framework\src\Illuminate\Database\Connection.php:459

  6   Illuminate\Database\Connection::statement("alter table `customer_orders` add constraint `customer_orders_customer_id_foreign` 
        foreign key (`customer_id`) references `customers` (`customer_id`
\\\\\\\\

当我删除外键时，一切正常。现在，我收到以下错误消息：

#include <stdio.h>
#include <stdlib.h>
extern void sum_col(int n, int m, long int *matrix[], long int new_col[]);
int main() {
    int n = 4, m = 3, i, j;
    long int *matrix[4];
    long int new_col[3];
    for (i = 0; i < n; i++)
        matrix[i] = (long int *)malloc(m * sizeof(long int));
    for (i = 0; i < n; i++)
        for (j = 0; j < m; j++)
            matrix[i][j] = 100 * i + j;
    sum_col(n, m, matrix, new_col);
    printf("matrix:\n");
    for (i = 0; i < n; i++) {
        for (j = 0; j < m; j++)  printf("%8ld", matrix[i][j]);
        printf("\n");
    } // for
    printf("new_col:\n");
    for (i = 0; i < m; i++)
        printf("%8ld", new_col[i]);
    return 0;
} // main

Answer 1

您应该在创建外键之前创建一个字段。例如，这应该起作用：

Schema::create('customer_order_products', function (Blueprint $table) {
    $table->increments('customer_order_product_id');
    $table->integer('order_id')->unsigned();
    $table->integer('product_id')->unsigned();
    $table->float('totaal_bedrag');
    $table->timestamps();

    $table->foreign('product_id')->references('product_id')->on('products');
    $table->foreign('order_id')->references('order_id')->on('customer_orders');
});

还要确保您的迁移以正确的顺序运行。 products和customer_orders的迁移应在上述迁移之前运行。

Laravel 5.7模式外键SQLSTATE [42000]迁移

1 个答案: