How to add a new user in a PL/SQL table using a function? - oracle

Question

I am fairly new to PL/SQL and one of the doubts I have is to create and declare functions.
Specifically this one:
Create a function that creates a new user:
Use a sequence togive the new User a new ID
Pass the name, address, etc... as IN arguments
Return as OUT arguments the ID created and a O_ERROR_MESSAGE
Function returns TRUE if the user is added, otherwise returns FALSE
Handle exceptions
Create a PL/SQL block and test the created function
This is my code so far:
CREATE OR REPLACE FUNCTION DSB_ADD_NEW_USERS (I_NAME IN VARCHAR2,
I_ADDRESS IN VARCHAR2,
I_BIRTHDATE IN DATE,
I_COUNTRY IN VARCHAR2)
RETURN NUMBER IS
O_ERROR_MESSAGE EXCEPTION;
CURRENT_USER NUMBER;
BEGIN
DSB_NB_SEQ_USER_ID.NEXTVAL;
SELECT COUNT(USER_ID) INTO CURRENT_USER
FROM DSB_NB_USERS;
WHILE CURRENT_USER != 0
LOOP
DSB_NB_SEQ_USER_ID.NEXTVAL;
SELECT COUNT(USER_ID) INTO CURRENT_USER
FROM DSB_NB_USERS;
END LOOP;
INSERT INTO DSB_NB_USERS (USER_ID, NAME, ADDRESS, BIRTHDATE, COUNTRY_ID_FK) VALUES (CURRENT_USER, I_NAME, I_ADDRESS, TO_DATE('I_BIRTHDATE', 'DD/MM/YYYY'), I_COUNTRY);
RETURN CURRET_USER;
EXCEPTION
WHEN O_ERROR_MESSAGE THEN
RETURN NULL;
WHEN OTHERS THEN
RETURN NULL;
END;
DECLARE
I_NEW_USER NUMBER;
BEGIN
I_NEW_USER := DSB_ADD_NEW_USERS(I_NAME => 'Arnaldo Amaral',
I_ADDRESS => 'Rua da Agra',
I_BIRTHDATE => '03/05/1959',
I_COUNTRY => 'PT');
END;
Am i too far from the truth?
I know there's still a lot to add.
Thank you for the help!!!

Answer 1

It seems to me you are asking for a lifeline, that needs more than just a code response. First off look at the answer by
#Tejash. His solution is a far cry from what you have, and is correct for your function definition (although that is itself incorrect given your listed requirements.) Also, #EdStevens is correct that is is a very poor use of a function. However a function is your assignment's requirement.
So lets dissect your code and see how it satisfies each of your requirements. (I cannot stand all caps, so I'm lower casing it.)
Fails. While you have a sequence it is used improperly. You can not
just code a standalone name. It must be used in either a SQL
statement or an assignment statement.
Passes.
Fails. Your function passes the IN parameters correctly. However
there are no OUT parameters.
Your function returns Number not the required True/False which
requires either Boolean or varchar2 for literal.
Code section for requirements 3,4.
create or replace function dsb_add_new_users (i_name in varchar2,
i_address in varchar2,
i_birthdate in date,
i_country in varchar2) <<< where are the 2 required out parameters
return number is <<< Should be True or False so either Boolean or varchar2
o_error_message exception; <<< Should be an Out parameter not an exception
Yes you have the Exception Section, which is required for handling
exceptions. However you do not handle exceptions so much as suppress
them, indicating to Oracle, and to the calling routine, that they didn't actually happen.
exception
when o_error_message then <<< as coded this is a developer defined exception, yet is not raised so it cannot happen.
return null; <<< even if it were raised you have thrown it away, the calling routine will never it happened
when others then <<< One of the worst pieces of code that can be written. I tend to remember seeing a discussion in
return null; <<< Oracle that would make this a compile time error. To bad the supporters lost the argument.
Passed, mostly. Correct for posted code, but insufficient per requirements.
So all-in-all not highly successful when viewed against the requirements.
A couple other items not specific the requirements, but disaster to successful implementation.
While technically you might get away with the following it is very bad practice. Current_User is an Oracle reserved word.
current_user number; <<< NO, NO bad verifiable name.
The following completely decimates your function. It creates a never ending loop. Well not quite -- it runs 1 time, but never afterward.
I believe you intended for the current_user variable to contain the ID assigned to the user. But it actually contains the number of rows in the table. Further what would the number of rows (count) have to do with Inserting a row? SO what does the code actually Do?
dsb_nb_seq_user_id.nextval; <<< systax error.
select count(user_id) into current_user <<< count the number of rows in the table
from dsb_nb_users;
while current_user != 0 <<< if there are any rows in the table
loop
dsb_nb_seq_user_id.nextval; <<< syntax error
select count(user_id) into current_user <<< try counting then again until there are none.
from dsb_nb_users;
end loop;
So correcting for the above what do we wind up with. I hesitate here in fear you will just copy the below and submit it. Please don't do that but study and understand what it's doing, then rewrite you routine. But after tearing you initial effort up, I guess I owe a corrected solution.
create or replace function dsb_add_new_users
( i_name in varchar2
, i_address in varchar2
, i_birthdate in date
, i_country in varchar2
, o_new_user_id out number
, o_error_message out varchar2
return boolean
is
country_id_l number;
begin
-- initialize out variables
o_new_user_id := null;
o_error_message := null;
-- get country id from input parameter
select country_id
into country_id_l
from country
where name = i_country;
-- create user and get the assigned user_id
insert into dsb_nb_users (user_id, name, address, birthdate, country_id_fk)
values dsb_nb_seq_user_id.nextval
, i_name
, i_address
, i_birthdate
, country_id_l
)
returning user_id
into o_new_user_id;
return true;
exception
when no_date_found then
o_output_message = 'ERROR: Specified country name ''' || country_id_l || ''' Not Found.';
return false;
when others then
o_output_message := 'ERROR: ' || sqlerrm;
return false
end dsb_add_new_users ;
--------------- Test Driver ----------------
declare
i_new_user number;
new_user_created boolean;
error_message varchar2(255);
begin
new_user_created := dsb_add_new_users( i_name => 'Arnaldo Amaral',
, i_address => 'Rua da Agra'
, i_birthdate => to_date('03/05/1959','mm/dd/yyyy') -- or is it 'dd/mm/yyyy'
, i_country => 'PT'
, o_new_user_id => i_new_user
, o_error_message => error_message);
if not new_user_created
then
dbms_output.put_line (error_messag);
end if ;
end;
Disclaimer: As you did not post table DDL nor test data the routine has not been tested nor even compiled. Any syntax error(s) is for you to resolve. Further, I follow Tejash in the assumption you actually have a countries table and there is a FK to it. That may be an erroneous assumption.

Answer 2

Why don't you directly use the sequence value to insert new user as follows:
CREATE OR REPLACE FUNCTION DSB_ADD_NEW_USERS (
I_NAME IN VARCHAR2,
I_ADDRESS IN VARCHAR2,
I_BIRTHDATE IN DATE,
I_COUNTRY IN VARCHAR2
) RETURN NUMBER IS
CURRENT_USER_ID NUMBER;
BEGIN
CURRENT_USER_ID := DSB_NB_SEQ_USER_ID.NEXTVAL; -- returns new and unique number
INSERT INTO DSB_NB_USERS (
USER_ID,
NAME,
ADDRESS,
BIRTHDATE,
COUNTRY_ID_FK
) VALUES (
CURRENT_USER_ID,
I_NAME,
I_ADDRESS,
I_BIRTHDATE,
(
SELECT
COUNTRY_ID
FROM
COUNTRIES
WHERE
NAME = I_COUNTRY
) -- it is FK so need to use SELECT sub-query to find COUNTRY_ID
);
RETURN CURRENT_USER_ID; -- returning the new user ID
EXCEPTION
WHEN OTHERS THEN
RETURN -1; -- returning -1 in case there is any error
END;
-1 will be returned when there is an error while adding the new user.

Answer 3

Came up with this much simpler answer after asking to a few people for help.
create or replace FUNCTION DSB_ADD_NEW_USERS (I_NAME IN VARCHAR2,
I_ADDRESS IN VARCHAR2,
I_BIRTHDATE IN DATE,
I_COUNTRY IN VARCHAR2)
RETURN NUMBER IS
CURRENT_USER NUMBER;
BEGIN
CURRENT_USER := DSB_NB_SEQ_USER_ID.NEXTVAL;
DBMS_OUTPUT.PUT_LINE('Hello World');
INSERT INTO DSB_NB_USERS (USER_ID, NAME, ADDRESS, BIRTHDATE, COUNTRY_ID_FK) VALUES (CURRENT_USER, I_NAME, I_ADDRESS, TO_DATE(I_BIRTHDATE, 'DD/MM/YYYY'), I_COUNTRY);
RETURN CURRENT_USER;
EXCEPTION
WHEN OTHERS THEN
RETURN -1;
END;
SET SERVEROUT ON
DECLARE
I_NEW_USER NUMBER;
BEGIN
I_NEW_USER := DSB_ADD_NEW_USERS(I_NAME => 'Arnaldo Amaral',
I_ADDRESS => 'Rua da Agra',
I_BIRTHDATE => '03/MAY/1959',
I_COUNTRY => 'PT');
commit;
END;
/
Thank you all!!!