Is not filter issue in Looker visualisation

[sysph]

When i use `is not` equal to  in the filter, it automatically add "or the same column  is null" in the SQL. How do i remove it or how shall i change my filter? 

thanks

[GavinW · Accepted solution]

I think the filter logic from Looker is correct - you are saying you don't want to see rows with 'A' or 'B' subscription status, but you are not excluding null results for subscription status, so you are telling Looker you want to see those rows too.

If you want to filter out nulls, which I think you are doing by adding 'none' to the filter, then you can add a new additional filter on the same field and set it to 'is not null'. Adding 'none' or 'null' to the original filter just tells Looker to filter out strings that have those values, not the 'NULL' special marker used to indicate cells with no value set.