Correlating Inline Views
Kim Berg Hansen · Apress eBooks · 2020
Most of the time in SQL, you can simply join tables or views to one another to get the result you want. Often you add inline views and scalar subqueries to the mix, and you can soon create relatively complex solutions to many problems. But scalar subqueries can only return a single column and inline views can normally not reference tables from outside; the workarounds to either can sometimes lead to inefficiencies. For both those problems, it has been possible since version 12.1 to solve them by correlating the inline view with lateral or apply.