Scalar functions
A scalar function can be used wherever an expression can be used. The restrictions on the use of aggregate functions do not apply to scalar functions, because a scalar function is applied to single set of parameter values rather than to sets of values. The argument of a scalar function can be a function. However, the restrictions that apply to the use of expressions and aggregate functions also apply when an expression or aggregate function is used within a scalar function. For example, the argument of a scalar function can be a aggregate function only if a aggregate function is allowed in the context in which the scalar function is used.
If the argument of a scalar function is a string from a column with a field procedure, the function applies to the decoded form of the value and the result of the function does not inherit the field procedure.
CURRENT DATE - BIRTHDATE
in each row of DSN8A10.EMP for which
the employee represented is in department D11: SELECT EMPNO, LASTNAME, YEAR(CURRENT DATE - BIRTHDATE)
FROM DSN8A10.EMP
WHERE WORKDEPT = 'D11';