I want errors of sql queries to the database to be visible in Grafana, for that i cannot use the database itself as it will be an erroneous circle. So is it possible to directly connect Nodered to Grafana?
I, for one, don't understand what you are asking, can you give more detail of what you mean please? Possibly an example of what is the situation that may occur and what you want to happen.
If it is possible to send nodered data directly to grafana, without the intervention of a database.
The only way (I know of) to get data into Grafana is through whatever data source you have configured in Grafana. It doesn't have its own database you can write to.
So if the database Grafana is configured to use is not available, then grafana cannot display any data.