Use an inline query in LookMl

Hi lovely people of Looker!

I’m trying to add a single result from a DT to each row of a table. I have been doing this using a CROSS join which does return the results I would expect however it is really inefficient and adds considerable time to my query.

I can speed this query up a lot in SQL by using an inline query from a CTE like the following

WITH CTE
AS (
SELECT SingleRowResult FROM ATable a WHERE [Filters are applied]
)
SELECT *,
( SELECT SingleRowResult FROM CTE ) AS SingleRowResult
FROM BTable b;

A little bit of background as to what I want to do this;

I need to calculate a percentage based off of my FILTERED population. So the DT I create returns the total population with all my filtered applied as a single value. I can then divide by this number to calculated my filtered %.

Is there a way I can do this in LookML?

Thanks all!