title: ORA-38104: Columns referenced in the ON Clause cannot be updated c.emp_id
body: <p>i have 2 simple table</p>
  
  <pre><code>CREATE TABLE employee (
    emp_id INT PRIMARY KEY,
    first_name VARCHAR(40),
    last_name VARCHAR(40),
    birth_day DATE,
    sex VARCHAR(1),
    salary INT,
    super_id INT,
    branch_id INT
  );
  
  CREATE TABLE biodata (
    emp_id INT PRIMARY KEY,
    first_name VARCHAR(40),
    last_name VARCHAR(40),
    birth_day DATE,
    sex VARCHAR(1)
  );
  </code></pre>
  
  <p>i want to merge it</p>
  
  <pre><code>merge into biodata c
  using employee e
  on (c.emp_id = e.emp_id)
  when matched then
    update set
    c.emp_id=e.emp_id,
    c.first_name=e.first_name,
    c.last_name=e.last_name,
    c.birth_day=e.birth_day,
    c.sex=e.sex
  when not matched then
    insert VALUES(e.emp_id,e.first_name,e.last_name,e.birth_day,e.sex);
  </code></pre>
  
  <p>but Oracle says:</p>
  
  <blockquote>
    <p><strong>ORA-38104:</strong> <em>Columns referenced in the ON Clause cannot be updated:</em>
    <strong><em>c.emp_id</em></strong></p>
  </blockquote>