问题
This might sound like an obvious question but I just want to get some reassurance.
Using Laravel's eager loading functionality, from what I understand it will create two queries to return a whole list of related results (say if you're working with two tables). However, and correct me if I'm wrong, using a join statement will leave you with only one query, which creates one less round trip to the server's database (MySQL) and is a more efficient query.
I know that you can write join queries in Laravel, which is great, so the question is: am I incorrect to assume that when retrieving related data from two or more tables, should I not bother with eager loading and instead just write my own join statements?
****** Edit *******
Coming back to this one year later, I'd say in my personal opinion, just write the queries, raw, and write them well.
回答1:
You are absolutely right about your understanding. If you write a join statement to join two or more tables using join() in Laravel then it makes only one query where using an Eloquent model with eager loading technique requires more than one query.
should I not bother with eager loading and instead just write my own join statements
Actually, the eager loading is a technique to load related models using Eloquent ORM easily and it uses Query Builder behind the scene and lets you use Eloquent Model Object without making the query by your self and represents the data differently, Using Eloquent ORM you are able to interact with model directly which represent objects in the database with additional features. Most importantly, it hides the complexity of SQL and allows you to do the database query in an OOP fashion using PHP code.
But when you manually call join method which belongs to Illuminate\Database\Query\Builder class then you are using the Query Builder directly which requires you write more code and requires more knowledge of sql query because it doesn't hide the query from you but helps you make queries more precisely, but you still make queries.
Both are different things and they work differently. You may search on Google using the term ORM vs Query Builder.
来源：https://stackoverflow.com/questions/24271416/laravel-eager-loading-vs-explicit-join