Procedure to insert data if not exist pl sql - sql

Question

I have a table with these columns (id,first_name,birth). I want to create a procedure that insert a new customer only if the id inserted doesn't exist in the table. If it already exist, then don't insert it. This is my code so far, but I got an error 'line 3 sql statement ignored'. Any idea? I need to use procedure and pl sql in oracle. Thanks!
CREATE OR REPLACE PROCEDURE add_emp(v_id IN int,
v_name IN varchar2,
v_bday IN date) IS
BEGIN
INSERT INTO Employees
(Id, First_name, Birth)
SELECT *
FROM (SELECT v_id, v_name, v_bday) AS tmp
WHERE NOT EXISTS (SELECT Id FROM Employees WHERE Id = v_id);
END;
/
DECLARE
m_id int := 3;
m_name varchar2 := 'John';
m_bday date := '16-Dec-1990';
BEGIN
add_cust(m_id, m_name, m_bday);
END;
/

Answer 1

Your procedure has some syntax issue which is fixed in following code:
CREATE OR REPLACE PROCEDURE ADD_EMP (
V_ID IN INT,
V_NAME IN VARCHAR2,
V_BDAY IN DATE
) IS
BEGIN
INSERT INTO EMPLOYEES (
ID,
FIRST_NAME,
BIRTH
)
SELECT V_ID,
V_NAME,
V_BDAY
FROM DUAL -- FROM clause was missing
WHERE NOT EXISTS (
SELECT ID
FROM EMPLOYEES
WHERE ID = V_ID
);
END;
/
Also, Your calling PL/SQL block has some issues which are corrected in the following code:
DECLARE
M_ID INT := 3;
M_NAME VARCHAR2(10) := 'John'; -- varchar2 must be declared with size
M_BDAY DATE := DATE '1990-12-16'; -- added date literal to convert string to date
BEGIN
ADD_CUST(M_ID, M_NAME, M_BDAY);
END;
/

Answer 2

In Oracle SELECT does not work without a FROM clause (other DBMS products are different). So you need to provide a table; you can use DUAL, which is a dummy table provided by Oracle which is guaranteed to return one row.
INSERT INTO Employees(Id,First_name,Birth)
SELECT v_id, v_name, v_bday
from dual
WHERE NOT EXISTS (
SELECT Id FROM Employees WHERE Id = v_id
);

Answer 3

Your INSERT statement would work with a slight change
CREATE OR REPLACE PROCEDURE add_emp(v_id Employees.Id%type,
v_name Employees.First_name%type,
v_bday Employees.Birth%type) IS
BEGIN
INSERT INTO Employees
(Id, First_name, Birth)
SELECT v_id, v_name, v_bday
FROM dual
WHERE NOT EXISTS (SELECT * FROM Employees WHERE Id = v_id);
END;
/
You can replace INSERT statement with MERGE as an alternative DML such as
MERGE INTO Employees e1
USING
(SELECT v_id AS id, v_name AS First_name, v_bday AS birth
FROM dual) e2
ON ( e1.id = e2.id )
WHEN MATCHED THEN UPDATE SET e1.First_name = e2.First_name,
e1.Birth = e2.Birth -- If you need to change for the matching case
WHEN NOT MATCHED THEN INSERT( e1.id, e1.First_name, e1.birth )
VALUES( e2.id, e2.First_name, e2.birth );