It's cooking and running for me.  Oddly, I find the more I cook, the more I have to run.

The assumption I've made is that HRID represents a Student OR an Employee. The employees represent the teaching staff, cleaners and caterers etc and the students are the actual pupils...

I see. It's logical that a function on the right of an ON (which is what I meant when I said WHERE clause above) won't affect SARGability.

It certainly...

 CREATE TABLE #items ---- Build test tables, credit to the great Jeff Moden for this bit.
(
    ItemID INT IDENTITY(101,1)
    ,Title VARCHAR(6)
)
ALTER TABLE...

You're welcome.  I've been caught out by that myself recently :blush:

I see.  I'm assuming your dropdowns are Report Parameters.  If that is the case, if you tick the Allow Multiple Values box thusly

then set your filter like...

You need to include the two columns in the #Temp table that you reference in the subquery. It doesn't matter that they are present in the permanent tables, they need...

Do you know when you've explained to a user at least twice that unless they fix their data and pay for the changes necessary to map two entities directly, the...

I'm absolutely sure that the data didn't change because the only person that could have changed it was me.  The report is based on a data warehouse that is loaded...