php – laravel migrate：回滚错误

Laravel版本5.1.43(LTS)

我使用PHP artisan migrate：在终端回滚然后返回错误消息.但数据库已更改.然后我再次重新输入此命令,没有错误消息.

任何人都可以帮我解决这个问题吗？

[Illuminate\Database\QueryException]
sqlSTATE[42000]: Syntax error or access violation: 1091 Can’t DROP’user_id’; check that column/key exists (sql: alter table crm_user drop index user_id)

[PDOException]
sqlSTATE[42000]: Syntax error or access violation: 1091 Can’t DROP ‘user_id’; check that column/key exists

我的迁移代码

public function down()
{
    if (Schema::hasColumn('crm_user', 'user_id')) {
        Schema::table('crm_user', function (Blueprint $table) {
            $table->dropColumn('user_id');
            $table->dropIndex('user_id');
        });
    }
}

解决方法:

删除列时会自动删除索引.因此,当您尝试单独删除索引时,您会收到不存在的错误.

因此,要么交换订单,要先删除索引：

$table->dropIndex('user_id');
$table->dropColumn('user_id');

或者只是删除列,不要担心索引.

从MysqL手册：

If columns are dropped from a table, the columns are also removed from any index of which they are a part. If all columns that make up an index are dropped, the index is dropped as well.