How to optimize a MySQL query?

Question

MySQL

There are 2 tables: A and B
A - 80,000,000 records
B - 10,000,000 records
Both have an id primary key.
Table B has a link to A (a_id). This reference can be null (NULL)
How to select ALL records from A and any row from B where the reference is not null?

Answer 1

left join