PL/SQL error question - sql

Question

I am trying to write a stored procedure that inserts a row into an employee table. If the department does not exist, that department needs to be inserted into the departments table. I have the following code:
drop table employees;
drop table departments;
create table departments(
dept varchar2(30),
dept_number number,
dept_city varchar2(30),
CONSTRAINT pk_dept PRIMARY KEY(dept)
);
create table employees(
dept varchar2(30),
employee_name varchar2(40),
employee_id number,
CONSTRAINT pk_id PRIMARY KEY(employee_id),
CONSTRAINT fk_dept FOREIGN KEY (dept) REFERENCES departments(dept)
);
CREATE OR REPLACE PROCEDURE employeeadd(
a_dept IN VARCHAR2,
a_employee_name IN VARCHAR2,
a_employee_id IN NUMBER)
as
li_count NUMBER;
BEGIN
sp_check_dept(a_dept, li_count);
if li_count = 0 then
INSERT INTO departments (dept) values (a_dept);
return;
end if;
INSERT INTO employee values (a_dept, a_employee_name, a_employee_id);
end;
/
create or replace procedure sp_check_dept(a_dept IN NUMBER,
a_count OUT NUMBER)
as
begin
select count(*)
into a_count
from departments
where dept_number = a_dept;
end;
/
When I run my execute statement as execute employeeadd('marketing', 'john', 10); I get the following errors. I can't seem to figure out how to get past the errors and/or write this correctly:
ORA-06502: PL/SQL: numeric or value error: character to number conversion error
ORA-06512: at "employeeadd", line 8
ORA-06512: at line 1

Answer 1

Why is li_count declared outside the BEGIN...END block? Do you need to assign it before sending it as an argument to sp_check_dept()?
Edit: Just saw your followup comment: sp_check_dept is expecting a number as its first parameter; you have declared a_dept as VARCHAR.

Answer 2

sp_check_dept takes a department number an input parameter (a NUMBER) and returns a count as an ouput parameter. employeeadd is passing a department name (a VARCHAR2) as the first parameter to sp_check_dept. There are a couple of ways to fix this. In general, you'll want a more consistent method of naming parameters to make it easier to identify these problems.
Option 1: Use the department name for both functions
create or replace procedure sp_check_dept(p_dept_name IN departments.dept%type,
p_count OUT NUMBER)
as
begin
select count(*)
into p_count
from departments
where dept = p_dept_name;
end;
/
CREATE OR REPLACE PROCEDURE employeeadd(
p_dept_name IN departments.dept%type,
p_employee_name IN employees.employee_name%type,
p_employee_id IN employees.employee_id%type)
as
li_count NUMBER;
BEGIN
sp_check_dept(p_dept_name, li_count);
if li_count = 0 then
INSERT INTO departments (dept)
VALUES (p_dept_name);
end if;
INSERT INTO employee(dept, employee_name, employee_id)
VALUES (p_dept, p_employee_name, p_employee_id);
end;
/
Option 2: Convert the department name in employeeAdd to the department number before passing it to sp_check_dept
create or replace procedure sp_check_dept(p_dept_number IN departments.dept_number%type,
p_count OUT NUMBER)
as
begin
select count(*)
into p_count
from departments
where dept_number = p_dept_number;
end;
/
CREATE OR REPLACE FUNCTION get_dept_number( p_dept_name IN departments.dept%tyep )
RETURN departments.dept_number%type
IS
l_dept_number departments.dept_number%type;
BEGIN
SELECT dept_number
INTO l_dept_number
FROM departments
WHERE dept = p_dept_name;
RETURN l_dept_number
END;
/
CREATE OR REPLACE PROCEDURE employeeadd(
p_dept_name IN departments.dept%type,
p_employee_name IN employees.employee_name%type,
p_employee_id IN employees.employee_id%type)
as
li_count NUMBER;
BEGIN
sp_check_dept( get_dept_number(p_dept_name), li_count);
if li_count = 0 then
INSERT INTO departments (dept)
VALUES (p_dept_name);
end if;
INSERT INTO employee(dept, employee_name, employee_id)
VALUES (p_dept, p_employee_name, p_employee_id);
end;
/
A couple of other observations
I removed the RETURN statement from your IF statement in employeeAdd. You almost certainly do not want to exit the procedure after inserting a row into the DEPARTMENTS table before inserting the row into the EMPLOYEE table.
Your table definition used the plural EMPLOYEES. Your procedure used the singular EMPLOYEE. I did not correct that because I wasn't sure whether the DDL you posted was incorrect or whether the procedure you posted was incorrect.
It would, in general, make far more sense for sp_check_dept to be implemented as a function that returned the count rather than as a procedure with an OUT parameter. If a piece of code simply exists to return data to the caller, it should be declared as a function.
From a data model standpoint, the column name DEPT isn't particularly good. It would be far more appropriate to use something like DEPARTMENT_NAME that conveys what the column actually represents.
From a data model standpoint, having the VARCHAR2 column DEPT (even if it is renamed to DEPARTMENT_NAME) as the primary key of DEPARTMENTS and the foreign key in EMPLOYEES does not make much sense. The primary key should be immutable. However the name of the department will change over time. It would make far more sense for the DEPARTMENT_NUMBER to be the primary key and for the DEPARTMENT_NAME to simply be marked as unique. That will make it far easier when the Marketing department gets renamed Advertising in the future because you won't have to chase down all the child tables to update them.
You should pick a naming convention for procedures and stick with that. I would prefer check_dept and add_employee (verb followed by subject, underscores separating words, no prefix). But if you wanted sp_check_dept and sp_add_employee or checkDept and addEmployee or even sp_dept_check and sp_employee_add that would be fine. But you'll drive yourself, and the other developers, crazy if there is no pattern to your procedure naming conventions.

Answer 3

2 possibilities I can see:
1. the employee table has columns in a different order than your insert statement and it's trying to convert dept or name to the id
2. the value set into li_count isn't a number so it's trying to convert the return value to a number and giving you the error