Here is the query I wrote, and it works correctly in the database. But it doesn’t work in Tableau Prep. How do I rewrite it? What are the syntax rules to make it work?

Here is the query I wrote, and it works correctly in the database. But it doesn’t work in Tableau Prep. How do I rewrite it? What are the syntax rules to make it work?

I am very new to the data world. I am hoping to gain more expertise in Tableau. Seeking a list of resources that could help me graduate from a beginner to an expert level.