A compound expression specifies a combination of other expressions.
You can use any built-in function as an expression (Function Expressions). However, in a compound expression, some combinations of functions are inappropriate and are rejected. For example, the
LENGTH function is inappropriate within an aggregate function.
PRIOR operator is used in
BY clauses of hierarchical queries.
COLLATE operator determines the collation for an expression. This operator overrides the collation that the database would have derived for the expression using standard collation derivation rules.
Some valid compound expressions are:
('CLARK' || 'SMITH') LENGTH('MOOSE') * 57 SQRT(144) + 72 my_fun(TO_CHAR(sysdate,'DD-MMM-YY')) name COLLATE BINARY_CI