Convert string to numeric value within Grafana

Hello everybody,
I am new to Grafana and have a problem regarding the format of my sql table “value” column.
If it is possible I would like to convert the values “open” and “closed” to numeric values within Grafana. Unfortunately my knowledge in this area is very limited.
If anyone has a “CONVERT(” function at hand to do this I would appreciate the help.

Via google I have found options within node-red, but I would prefer a Grafana alternative.

Just FYI
The Table:
The Panel:

Click on EDIT SQL and the next query would do. It will return 1 when the string is open and 0 when it is closed

SELECT IF(value = “open”, 1, 0)

I have a similar doubt but my table has numeric values stored in string and grafana v5.3.4 is not able to plot those values as they are string. Grafana shows the same error as the one showed by @nighthawk

So the column contains values like: “764.78” , “703.2”.

Could someone please help me out with this?