title: How do I combine projection and selection operators in relational algebra?
body: <p>So I have this query in SQL that tells me to find two columns in a table where a certain condition is met, but I have to convert this query into relational algebra form.</p>
  
  <p>Let's say I have to select a name and an address from a table (People) where the person is older than 18.</p>
  
  <p>My only thoughts currently are to write this:</p>
  
  <pre><code>Select name,address from People where age&gt;18
  </code></pre>
  
  <p>... which would theoretically translate to this:</p>
  
  <pre><code>π name,address σ age&gt;18 (People)
  </code></pre>
  
  <p>Is this correct?</p>