Help with creating filter on analysis for learning initiative

Summary

Help with creating filter on analysis for learning initiative

Content

Hi 

Apologies if this is a stupid question...

We want to start using learning initiatives to auto enrol new staff onto training. What filter should I apply to the 'Work Relationship Start Date' field so that only people starting on that particular day appear on the analysis. I'm assuming the learning initiative just runs once per day?

We were told to use the SQL expression below, but it doesn't work:

TIMESTAMPADD(SQL_TSI_Day , -1, current_date)