Laravel Eloquent - 选择 MAX 与其他列
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Laravel Eloquent - Select MAX with other columns
提问by Jean-Luc Tallis
I'm trying to select a number of columns along with MAX. The raw query would be something like: SELECT users.id, ..., MAX(ur.rank) AS rankbut I cannot figure out how to do it using the query builder supplied by Laravel in Eloquent.
我正在尝试与 MAX 一起选择一些列。原始查询类似于：SELECT users.id, ..., MAX(ur.rank) AS rank但我无法弄清楚如何使用 Laravel 在 Eloquent 中提供的查询构建器来完成它。
This is my attempt:
这是我的尝试：
$user = User::join('users_ranks AS ur', function($join) {
$join ->on('ur.uid', '=', 'users.id');
})
->where('users.id', '=', 7)
->groupBy('users.id')
->first(['users.id', 'users.username', 'MAX(ur.rank) AS rank']);
I simply cannot figure it out. What I want to achieve is I'm selecting a user where users.id = 7, and I'm wanting to select the MAX rank that's in users_ranks where their users_ranks.uid = users.id.
我简直想不通。我想要实现的是我选择一个users.id = 7的用户，我想选择users_ranks中的最大排名，他们的users_ranks.uid = users.id。
I was told to avoid sub-queries as when working with large result sets, it can slow things down dramatically.
我被告知要避免子查询，因为在处理大型结果集时，它会显着减慢速度。
Can anyone point me in the right direction? Thanks.
任何人都可以指出我正确的方向吗？谢谢。
回答by M0rtiis
I think you should rewrite it like this:
我认为你应该像这样重写它：
DB::table('users')
->select(['users.id', 'users.username', DB::raw('MAX(ur.rank) AS rank')])
->leftJoin('users_ranks AS ur', 'ur.uid', '=', 'users.id')
->where('users.id', '=', 7)
->groupBy('users.id')
->first();
No sense to use User::if you use table names later and want to fetch not all of the fields ( 'users.id', 'users.username').
User::如果您稍后使用表名并且不想获取所有字段 ( 'users.id', 'users.username') ，则使用没有意义。
