title: How to combine two fields and flag them accordingly
body: <p>I would like to know how to flag customers who did not purchase some items that are described by two fields (product name and product number). I was able to perform this query for customers that did purchase them, but not the opposite. Thank you in advance for your help!</p>
  
  <p>Here is part of my SQL query.</p>
  
  <pre><code>Select customer_id, product_name, product_number
  from table 
  where 
  ((PRODUCT_NAME = 'LIAM' AND PRODUCT_NUMBER = '212') OR
   (PRODUCT_NAME = 'ARRAY' AND PRODUCT_NUMBER = '325') 
  )
  </code></pre>
  
  <p>Here is an example:</p>
  
  <pre><code>1 LIAM 212
  
  1 STACY 452
  
  1 NEIL 789
  
  1 LIAM 345
  
  2 ROSE 234
  
  2 LIAM 345
  
  2 ARRAY 325
  
  3 STACY 452 
  
  3 ARRAY 625
  </code></pre>
  
  <p>Query Result:</p>
  
  <pre><code>1 ARRAY 325
  
  2 LIAM 212
  
  3 ARRAY 325
  
  3 LIAM 212
  </code></pre>