Looking for one-to-one and one-to-many native query statements in Laravel

Question

Route::get('test', function () {

DB::connection()->enableQueryLog();

// Get the executed query array

Users::with('posts')->get();
dd(DB::getQueryLog());

});

array:2 [▼
0 => array:3 [▼

"query" => "select * from `users`"
"bindings" => []
"time" => 2.76

]
1 => array:3 [▼

"query" => "select * from `posts` where `posts`.`users_id` in (?, ?)"
"bindings" => array:2 [▶]
"time" => 0.71

]
]

In the above code, why not select id from user and then use this query result in the next step?

Answer 1

`select * from users` 可以获得users的所有数据
`select * from `posts` where `posts`.`users_id` in (?, ?)` 
可以把上一条语句的id放入in()获得posts表里users_id匹配的数据，接下来就可以用php来拼接数据，这样只要两条sql。
如果用select * from `posts` where `posts`.`users_id` in（select id from user）那么使用了自查询不说，而且users表的字段要怎么查询？
以上，个人理解，欢迎打脸！