In addition to the join condition in the ON clause, you can add further filters to a join query.
For example, say you want to publish only prices for trades of more than a 1000 shares.
Exercise
Add a WHERE clause to your join query that filters out all rows of less than 1000 from the TradesWindow Volume column. The WHERE clause comes after the ON clause and before the semi-colon (;) at the end of the statement. Restart the project and look at the output. What happens? Notice whether or not rows that do not match the join criteria are published. What does this tell you about the order in which the WHERE clause processes rows in relation to the ON clause and the SELECT clause? Stop the project.