在具有关系的 Laravel Eloquent 查询构建器中使用 UNION 和 DISTINCT

Question

我有两张桌子，

properties
+----+-----------+
| id | parent_id |
+----+-----------+
|  1 | null      |
|  2 | 1         |
|  3 | null      |
|  4 | 3         |
|  5 | 3         |
|  6 | null      |
+----+-----------+

和

sale_services
+----+-------------+------+
| id | property_id | rank |
+----+-------------+------+
|  1 |           2 |    5 |
|  2 |           4 |    4 |
|  3 |           5 |    6 |
|  4 |           6 |    7 |
+----+-------------+------+

和相应的 Eloquent 模型（SaleService 和 Property）通过关系（sale_service.property_id = property.id）相互链接。 Property 可以链接到同一个表中的另一个 Property。

我需要获取 SaleService 实例的集合，其中相关的 property.parent_id 为空，或者 sale_services 表中的某些记录共享相同的 parent_id 到 properties 表，区分按该字段并按rank 排序。

结果应该是

+----+-------------+------+
| id | property_id | rank |
+----+-------------+------+
|  1 |           2 |    5 |
|  3 |           5 |    6 |
|  4 |           6 |    7 |
+----+-------------+------+

- sale_services 表中的所有项目，除了 (sale_service.id = 2)，因为它的属性与项目 (sale_service.id = 3) 共享相同的 parent_id > 并且具有 (sale_service.id = 3) 的项目具有最高的rank 值

我想出了 SQL 代码来得到想要的结果，

 SELECT *
    FROM
      (SELECT DISTINCT ON (properties.parent_id) *
       FROM "sale_services"
       INNER JOIN "properties" ON "sale_services"."property_id" = "properties"."id"
       WHERE ("properties"."parent_id") IS NOT NULL
       ORDER BY "properties"."parent_id", "sale_services"."rank" DESC) AS sub
    UNION
    SELECT *
    FROM "sale_services"
    INNER JOIN "properties" ON "sale_services"."property_id" = "properties"."id"
    WHERE ("properties"."parent_id") IS NULL

但我无法使用 Eloquent Builder。

我试过这样的

$queryWithParent = SaleService::query()
    ->select(\DB::raw('DISTINCT ON (properties.parent_id) *'))
    ->whereNotNull('properties.parent_id')
    ->join('properties', 'sale_services.property_id', '=', 'properties.id')
    ->orderBy('parent_id')
    ->orderBy('sale_services.index_range', 'desc');

$queryWithoutParent = SaleService::query()
    ->join('properties', 'sale_services.property_id', '=', 'properties.id')
    ->whereNull('properties.parent_id');

$query = $queryWithParent->union($queryWithoutParent);

但出现错误

SQLSTATE[42601]: Syntax error: 7 ERROR: syntax error at or near "union" LINE 1: ...perties.type <> 'hotel') order by "parent_id" asc union sele... ^ (SQL: select DISTINCT ON (properties.parent_id) * from "sale_services" inner join "properties" on "sale_services"."property_id" = "properties"."id" where ("properties"."parent_id") is not null and ("sale_services"."deleted_at") is null and "published" = 1 and exists (select 1 from "properties" where properties.id = sale_services.property_id AND properties.type <> 'hotel') order by "parent_id" asc union select * from "sale_services" inner join "properties" on "sale_services"."property_id" = "properties"."id" where ("properties"."parent_id") is null and ("sale_services"."deleted_at") is null and "published" = 1 and exists (select 1 from "properties" where properties.id = sale_services.property_id AND properties.type <> 'hotel') order by "index_range" desc limit 12 offset 0)

如果我从第一个查询 ($queryWithParent) 中删除排序，它似乎可以正常工作，但在不同的查询中选择了随机项目。

有没有其他方法可以达到相同的结果，或者我做错了什么？

Answer 1

“Distinct”的 laravel 查询创建器是 distinct()，如：

$queryWithParent = SaleService::query()
->distinct('properties.parent_id')
->whereNotNull('properties.parent_id')
->join('properties', 'sale_services.property_id', '=', 'properties.id')
->orderBy('parent_id')
->orderBy('sale_services.index_range', 'desc');

这行得通吗？

Answer 2

终于找到了解决办法。

1. 使用 Laravel ^5.7.28（Laravel 5.7.28 中已修复 UNION 问题：github.com/laravel/framework/pull/27589），您将不需要子查询！

2. 指定要选择的表列以避免列名冲突sale_services.*

   $queryWithParent = SaleService::query()
       ->select(\DB::raw('DISTINCT ON (properties.parent_id) sale_services.*'))
       ->from('sale_services')
       ->join('properties', 'sale_services.property_id', '=', 'properties.id')
       ->whereNotNull('properties.parent_id')
       ->orderBy('properties.parent_id')
       ->orderBy('sale_services.index_range', 'desc');
   
   $queryWithoutParent = SaleService::query()
       ->select(\DB::raw('sale_services.*'))
       ->join('properties', 'sale_services.property_id', '=', 'properties.id')
       ->whereNull('properties.parent_id');
   
   $query = $queryWithParent->union($queryWithoutParent);