file/app/Rules/UniqueRule.php

<?php

namespace App\Rules;

use Illuminate\Contracts\Database\Query\Builder;
use Illuminate\Contracts\Validation\Rule;
use Illuminate\Support\Facades\DB;

class UniqueRule implements Rule
{
    private string $table;
    private string $field;
    private Builder $query;

    public function __construct(string $table, string $field)
    {
        $this->table = $table;
        $this->field = $field;
        $this->query = DB::table($this->table);
    }

    /**
     * Determine if the validation rule passes.
     *
     * @param string $attribute
     * @param mixed $value
     * @return bool
     * @throws \Throwable
     */
    public function passes($attribute, $value)
    {
        throw_if(is_array($value), 'UniqueRule won\'t work in array values like ' . $attribute);

        return empty($value) ? true : !$this->query->where($this->field, $value)->exists();
    }

    public function withoutTrashed($deletedAtColumn = 'deleted_at'): UniqueRule
    {
        $this->query->whereNull($deletedAtColumn);

        return $this;
    }

    public function where($column, $value): UniqueRule
    {
        $this->query->where($column, $value);

        return $this;
    }

    public function ignore($id): UniqueRule
    {
        if (empty($id)) {
            return $this;
        }
        $this->query->whereNot('id', $id);

        return $this;
    }

    /**
     * Get the validation error message.
     *
     * @return string
     */
    public function message()
    {
        return 'select value already exists.';
    }
}