title: SQL how do you find value that does not exist on same table?
body: <p>So we have columns order_number, product_name, product_number, product_type. product_type has two types, semi and finish and order number for semi starts with S and order number for finish type starts with F. Order numbers are like S123, F123. Semi and Finish order numbers exactly same except for starting part with SXXX for semi and FXXX for finish product type. They share same product name and product number but it can have 1 semi, 1 finish or just 1 semi with 1 finish product for each product number. How do I make query so I can find product that only exist in semi but not finished?</p>
  <p>I would query</p>
  <pre><code>SELECT ORDER_NUMBER, PRODUCT_NAME, PRODUCT_NUMBER
  FROM TABLE A
  WHERE PRODUCT_TYPE = 'SEMI'; 
  </code></pre>
  <p>but this does not show whether this product only exist in semi not finish. How do I pull this off? I can't just use PRODUCT_TYPE NOT IN ('FINISH') as their order numbers are different and only thing that matches are product name and product number.</p>
  <p>Help. :(</p>