Mysqli join tables from 2 different databases

Question

How Can I use this 2 connections to run a query which joins 2 tables? yesno.table1 and sushi.table1 ? lets say we join by id they both have the same id. how can I do that?

// Connect to Yesno Database
$this->yesno_db = new mysqli("red", "yesno", "***", "yesnotmp");

if ($this->yesno_db->connect_errno) {
    throw new Exception('Connection failed: '.$this->yesno_db->connect_error);
}   

// Connect to Sushi Database
$this->sushi_db = new mysqli("red", "sushi", "***", "sushi");

if ($this->sushi_db->connect_errno) {
    throw new Exception('Connection failed: '.$this->sushi_db->connect_error);
}

Answer 1

This question has nothing to do with mysqli (or any other API).

To do a join with a table from different database, a user which connects to mysql, have to have SELECT rights for both databases.

Having this done, just select one of databases in your connection statement and address another using usual dot syntax:

SELECT * FROM t1 JOIN db2.t2

To answer your question literally,

Can I use this 2 connections to run a query which joins 2 tables?

You can't