how can we code in code background without a real table to test whether the code is correct or NOT ?

Answer 1

If you want to check if the Syntax is correct you need a tool to do that for example: https://www.piliapp.com/mysql-syntax-check/

You can simulate queries by using a TRANSACTION, check the result and then ROLLBACK so it does not save.

You can check how a script would function by using DESCRIBE in front of the query.

Answer 2

We can use #tables which will store the data temporarily. they will be deleted from the database once the ongoing session is closed. they are also called as temp tables