set sql variable before main query

@ash-f,

Yes, it is possible to set sql variable before other queries.  The catch is...not the way you have it in your example.  There are a couple of ways that you could do it but you would have to use $this->db->query().  With one of those ways, you could actually do it in one query but again it is using the $this->db-query();

Thanks.
I saw something similar and they are using transaction with multiple $this->db-query().
So is that the standard way?