If I have a Model B that belongsTo Model A and I ask for Model A with Model B it would be more efficient to pull Model A with a join Model B.
I am using DebugBar and seeing that it issues 2 sql statements; one to retrieve Model A and one to retrieve Model B.
It is more efficient to pull Model A with a join of Model B so there is only 1 hit on the DB instead of 2.
You're overthinking this there are two styles of doing this one is as you suggest the other is like a monthly report.
For example company A with their receivables Company B and their receivables Etc.
Join is used a lot with a group by for a different style of report.
The two query technique is more like an invoice with the order details. In other words a Master detail or parent-child relationship.
So it depends on what data you need and how you need it.
See my answer here
I see your point, but if you have thousands of users on an application; it is more efficient for a one query solution or a two query solution?
The one extra query to get parent (master) is no big deal even if millions of users.
A join has to transverse over two tables.
You might want to take a basic sql tutorial. Or study the various selects, joins, etc here.
https://dev.mysql.com/doc/refman/8.0/en/
Again it depends on what data you need and how needed.
consider model A has 10 columns of data, and you are interested in 1 model
consider model B has 10 columns and there are 100 rows belonging to column A
with two queries, in memory you have two simple queries and one instance of A and 100 instances of B
with a join, you have 100 records in memory but all the columns of model A are duplicated over and over
so, separate queries might seem more inefficient but they are simpler and quicker than joining tables, and can be far more memory efficient
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