Please note that SQL Variables are supported in pure SQL. Here is an example notebook. https://github.com/rchynoweth/DemoContent/blob/main/Misc/SQL_Variables.sql

The syntax would be something like the following:

SET var.database_name = my_database ; 
 
SELECT * FROM ${var.database_name}.my_table; 
 

Note that the "var" can be any string i.e. it can be c.var_name instead.