title: MySQL check if multiple rows exist
body: <pre><code>Here you can find how to check row existance:
  SELECT EXISTS(SELECT 1 FROM table1 WHERE some_condition);
  </code></pre>
  
  <p>How to efficiently existance of multiple rows from table like:</p>
  
  <pre><code>SELECT EXISTS(SELECT 1 FROM table1 WHERE key = 0);
  SELECT EXISTS(SELECT 1 FROM table1 WHERE key = 2);
  </code></pre>
  
  <p>from table:</p>
  
  <pre><code>key,username
  0,foo
  1,bar
  2,boo
  </code></pre>
  
  <p>to return positive only if both rows (with key 0 and 2) was found?</p>