title: Understanding use of where in subqueries
body: <p>List the name and continent of countries in the continents containing either Argentina or Australia. Order by name of the country.</p>
  <p><a href="https://i.stack.imgur.com/XT92L.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XT92L.png" alt="enter image description here" /></a></p>
  <blockquote>
  <p>From <a href="https://sqlzoo.net/wiki/SELECT_within_SELECT_Tutorial" rel="nofollow noreferrer">https://sqlzoo.net/wiki/SELECT_within_SELECT_Tutorial</a>, question 3</p>
  </blockquote>
  <p>This is what I tried</p>
  <pre><code>select name, continent
  from world
  where continent = (select continent 
     from world where name in ('Argentina',' Australia'))
  order by name
  </code></pre>
  <p>Thought it was about equivalence, so tried this</p>
  <pre><code>select name, continent
  from world
  where continent in (select continent 
     from world where name in ('Argentina',' Australia'))
  order by name
  </code></pre>
  <p>and this seems to be the solution</p>
  <pre><code>select name, continent
  from world
  where continent = (select continent 
     from world where name ='Argentina')
  or continent = (select continent 
     from world where name ='Australia')
  order by name
  </code></pre>
  <p>I'm trying to understand the logical flaw in my solution.</p>