A compound expression is an expression that is a combination of other types of expressions.
You can use a built-in function as an expression. However, in compound expressions, some combinations of functions are inappropriate and are discarded. For example, the LENGTH function is inapplicable in an aggregate function.
You can use the PRIOR operators in the CONNECT BY clauses of hierarchical queries.
The following list provides some valid compound expressions:
('CLARK' || 'SMITH')LENGTH('MOOSE') * 57SORT(144) + 72my_fun(TO_CHAR(sysdate, 'DD-MMM-YY'))