嵌套预加载特定列

Question

当我这样做时

$category = NewsCategory::whereSlug($slug)->with('news.category:id,title,slug')->firstOrFail();

然后我有以下疑问

select * from `news_categories` where `slug` = 'novinki' limit 1
select * from `news_posts` where `news_posts`.`category_id` in (2) and `news_posts`.`deleted_at` is null
select `id`, `title`, `slug` from `news_categories` where `news_categories`.`id` in (2)

但我也想在第一个新闻关系中加载特定的列，如果我这样做会出错

$category = NewsCategory::whereSlug($slug)->with('news:id,title,image.category:id,title,slug')->firstOrFail();

获取此查询的正确方法是什么？

select * from `news_categories` where `slug` = 'novinki' limit 1
select `id`, `title`, `image` from `news_posts` where `news_posts`.`category_id` in (2) and `news_posts`.`deleted_at` is null
select `id`, `title`, `slug` from `news_categories` where `news_categories`.`id` in (2)```

Answer 1

我会将急切加载的关系放入一个数组中

试试这个：

$category = NewsCategory::whereSlug($slug)
              ->with([
                  'news:id,title,image,category_id,deleted_at',
                  'news.category:id,title,slug'
              ])->firstOrFail();

或者根据我个人的喜好，使用闭包来扩展查询，如下所示：

$category = NewsCategory::whereSlug($slug)
              ->with([
                  'news' => function($query){
                      $query->select('id','title','image','category_id','deleted_at');
                   },
                  'news.category' => function($query){
                      $query->select('id','title','slug');
                   }
              ])->firstOrFail();

嵌套预加载特定列

Nested Eager Loading Specific Columns

laravel

eloquent

eager-loading