Is it possible to build a filter with wql to query whether a specific environment variable exists?

I want to query a environment variable which I created. The request is to create it with the WMI. Since it is only possible to work with WQL there the "EXISTS" statement does not exist :D So I have to find another way but I have no idea what else I could try..

The SQL-Statement: SELECT * FROM win32_environment WHERE EXISTS(SELECT * FROM win32_environment WHERE name = "myVariable")

The error:

Number: 0x80041017 Institution: WMI Description: The request is invalid.