oracle11g - How do I check table to see if row already exists before inserting?

Question

This is my script. Trying to determine the best way to check if the row already exists by comparing the deptno

CREATE OR REPLACE PROCEDURE insert_rows
    (pl_deptno dept.deptno%TYPE, pl_dname dept.dname%TYPE, pl_loc dept.loc%TYPE
    ) AS
    BEGIN
    INSERT INTO dept 
    (deptno,dname,loc) 
    values ( pl_deptno,pl_dname,pl_loc);
    end insert_rows;
    /

Answer 1

If deptno is a unique key, just insert a row. If there is a duplicate, catch the exception and do what is needed.

Otherwise, you get all kinds of race conditions that require transactions to handle if two users are inserting/checking at the same time.