title: JOIN NOT DISPLAYING ALL RECORDS
body: <p>I'm sure that this is pretty obvious but I am completely stuck as I have never seen this before.</p>
  
  <p>I have a data set that can vary against a list of categories (6 in total). Some clients will have 1 or 2 categories other all 6. The information I'm trying to pull through is designed to pull through all 6 categories with the corresponding information depending on the client.</p>
  
  <p>So I have set up a simple mapping table with ID (1 to 6) and Category. I'm then joining this to my client data. The test data I'm using has categories 1,2,3,5 and whilst I get a NULL of 6 I get nothing for 4. I should see a Null row on category 4 as it doesn't exist in the client data?</p>
  
  <pre><code> SELECT *
  
  FROM .dbo.Lookup_Category C
  
  LEFT JOIN dbo.Client CL ON C.ID = CL.Category
  
  WHERE CL.ID = 423 OR CL.Category IS NULL 
  </code></pre>