title: Prevent Duplicate Insert Data in Oracle
body: <p>i have table COBA with 3 fields, they are NOMER, NAMA, KETERANGAN. in table there are exist data like this:</p>
  
  <p><a href="https://i.stack.imgur.com/Ki3uS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Ki3uS.png" alt="table COBA"></a></p>
  
  <p>i wanna insert another values to that table, but how can i prevent duplicate insert query data in oracle?
  i have tried use WHERE NOT EXIST, this is my query:</p>
  
  <pre><code>INSERT INTO COBA(NOMER, NAMA, KETERANGAN)
  (SELECT '2','FIAN', 'JEKULO'
  FROM DUAL
  WHERE NOT EXISTS (SELECT * FROM COBA WHERE NOMER='1' AND NAMA='AMIN' AND KETERANGAN='JEPARA'))
  </code></pre>
  
  <p>that query didn't work....any suggest for me,...thanks...</p>