title: Return rows even if record does not exist LEFT OUTER JOIN
body: <p>I have 2 tables below:</p>
  
  <pre><code>Table_1
  [Group No] [Test No] [Description]
  123        1         [First Test]
  123        2         [Second Test]
  123        3         [Third Test]
  
  Table_2
  [Sample No] [Test No] [Result Description]
  ABC         1         [Some More Result]
  ABC         3         [Some Result]
  DEF         1         [A Result]
  DEF         2         [Results More]
  DEF         3         [Bad Results]
  </code></pre>
  
  <p>Here's my query:</p>
  
  <pre><code>SELECT Table_1.[Group No], Table_1.[Test No], Table_1.Description, Table_2.[Result Description]
  FROM Table_1 
  LEFT OUTER JOIN Table_2 ON Table_1.[Test No] = Table_2.[Test No]
  WHERE (Table_1.[Group No] = '123') AND (Table_2.[Sample No] = 'ABC')
  </code></pre>
  
  <p>djacobson's query:</p>
  
  <pre><code>SELECT Table_1.[Group No], Table_1.[Test No], Table_1.Description, Table_2.[Result Description]
  FROM Table_1 
  LEFT OUTER JOIN Table_2 ON Table_1.[Test No] = Table_2.[Test No]
  WHERE (Table_1.[Group No] = '123') 
    AND (Table_2.[Sample No] IS NULL OR Table_2.[Sample No] = 'ABC')
  </code></pre>
  
  <p>This returns:</p>
  
  <pre><code>[Group No] [Test No] [Description] [Result Description]
  123        1         [First Test]  [Some More Result]
  123        3         [Third Test]  [Some Result]
  </code></pre>
  
  <p>But what I really want is:</p>
  
  <pre><code>[Group No] [Test No] [Description] [Result Description]
  123        1         [First Test]  [Some More Result]
  123        2         [Second Test] NULL
  123        3         [Third Test]  [Some Result]
  </code></pre>
  
  <p>Is this possible? I would like to return the record with Test No 2. However, how do I join to a record which is non-existent? Or is this simply not possible? What are the alternatives?</p>