Answer Posted / ankush

Function always return a value. procedure may or may be not.
IN a select statement function may be called but we should
execute the procedure.

We can call a stored function from dml statement.

Here is simple example


CREATE OR REPLACE FUNCTION TEST_1 RETURN NUMBER IS

BEGIN

RETURN(10);

END;


SELECT TEST_1 FROM DUAL;


update emp

set sal = sal+ sal*test_1();


To be called from an sql statement a function should follow
the following purity rules.
1) When called from a SELECT statement , the function
should not modify database objects.
2) When called from INSERT , UPDATE, DELETE statements ,
the function can not query or modify the tables that was
modified by the statement.
3)When called from SELECT , DELETE, UPDATE, INSERT
Statements , a function should not contain TCL, DDL
commands.

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