Complex SQL Query Breakdown Step By Step

 <https://www.youtube.com/watch?v=f1vuGPuug9s&ab_channel=DatabaseStar>

03:02

use the FROM clause to understand tables in the query

 04:60

LEFT JOIN (only join items into the union from the left table) uses a subquery where we can SELECT inside and the JOIN it on a field to the computed table

 08:50

any filters? HAVING is filtering where sum values != 0

 14:34

Run the main query in parts

Post Mortem