As the focus blurs away from data management and sound relational practices, data quality will deteriorate and productivity will decline. And then a new era of SQL vitality will arise. The Glow of the Future SQL is still a growing and very adaptable language. Depending on the version and flavor of DB2 you are using, new functionality such as CASE statements, outer joins, and nested table expressions have increased the number of tasks we can perform using SQL alone. But these features are not the end of how SQL will adapt to change.
Recursion enables a table expression to refer to itself.
To help you understand recursion better, think of the following metaphor. You can see the person multiple times in the picture because it is recursive. It is possible to traverse hierarchies such as a bill of materials or an organization chart using a single recursive query. Traditionally, DBMS products stored data and nothing else. An active database can take actions automatically and implicitly by virtue of an event occurring.