Declaring user variable into database using mysql connector c++ (2 replies)

Hello to Everyone,

I am developping a software using c++ and MySQL(for the database). I am currently having the issue that I don't find anything online on how to define
user variables like "@returnValue". Since I want like in all my previous experiences to keep a return status to all my call procedures, I would really like for consistency to have a solution for this. I am also under the impression that many other will have the same questions as they seem to be some links on Google for MySQl Connector/Net but not for c++.
I have tried lines similar to the following:

"SET @ReturnValue ='';"
or
"SET @ReturnValue = STR_TO_DATE('2021-5-13 3:5:9','%Y-%m-%d %H:%i:%S');

They work fine using a mysql console client but not when executing these statements (or prepared statements) under c++.
Have somebody found a workaround or solution for this!?

Thanks a lot in advance!

Armand