title: How to SUM the value of the specific rows only?
body: <p>Would like to get the SUM of two specific rows in a table in mysql.</p>
  
  <pre><code>create table people(
      id int,
      firstname varchar(50),
      money int
  );
  
  id   firstname    money
  1    david        100
  2    jack         200
  3    bob          300
  </code></pre>
  
  <p><strong><em>Say I want the SUM of row 1(david) and row 3(bob) only. The total should be 400.</em></strong></p>
  
  <p>I used this query:</p>
  
  <pre><code>SELECT SUM(money) 
  FROM people 
  WHERE id = 1 AND 3;
  </code></pre>
  
  <p>but it turned out to be <strong>100</strong>, and not <strong>400</strong> as I expected.</p>