Database

1. Procedure may or may not return value where as function should return one value.

2. Function can be called from SQL statement where as procedure can’t be called from the SQL statement.

3. Function are normally used for computation where as procedure are normally used for executing business logic.

4. Stored procedure is pre-compiled execution plan where as function are not.

5. We can call function within procedure but we can not call procedure within function.

6. A FUNCTION must be part of an executable statement, as it cannot be executed independently, whereas procedure represents an independent executable statement.

and for example of both syntax of function and procedure :

[code]CREATE OR REPLACE PROCEDURE test_proc
(p_id IN VARCHAR2) as begin … end

CREATE OR REPLACE FUNCTION test_func
(p_id IN VARCHAR2) return varchar2 as begin … end[/code]

hope this help.

one example to create a function to return ‘Y’ if parameter value is number otherwise which is exception in this case to return (‘N’)

ex:

[code]CREATE OR REPLACE FUNCTION is_number (p_string IN VARCHAR2)
RETURN VARCHAR2
DETERMINISTIC
PARALLEL_ENABLE
IS
l_num NUMBER;
BEGIN
l_num := TO_NUMBER (p_string);
RETURN ‘Y’;
EXCEPTION
WHEN VALUE_ERROR
THEN
RETURN ‘N’;
END is_number;[/code]

and here you can call the function created above to identify the value passed is number or not like :

[code]SELECT (CASE
WHEN (is_number (mycolumn) = ‘Y’)
THEN
‘your column value is number’
ELSE
‘your column value is not number’
END)
FROM myTable;[/code]

hope this help you.

You can find the following view to access all metadata about the columns :

user_tab_cols; — For all tables owned by the user

all_tab_cols ; — For all tables accessible to the user

dba_tab_cols; — For all tables in the Database.

and lets consider you want to add new column only if doesn’t exists you can use this pl/sql to check and add new column

[code]DECLARE
v_column_exists number := 0;
BEGIN
Select count(*)
into v_column_exists
from user_tab_cols
where column_name = ‘ADD_COLUMN’
and table_name = ‘departments’;

if (v_column_exists = 0) then
execute immediate ‘alter table departments add (ADD_COLUMN NUMBER)’;
end if;
end;[/code]

hope this help.