title: Behavior Changes on SELECT
body: <p>I'm migrating a SQL Server 2008 database to SQL Server 2019, I have used Microsoft Data Migration Assistant, to look for search any behavior changes, issues or syntax errors.</p>
  <p>I have a SELECT that gives me compatibility errors to do the migration:</p>
  <blockquote>
  <p>Object uses the old style join syntax which can have poor performance at database compatibility level 90 and higher.</p>
  </blockquote>
  <p>This is my SELECT that I think makes the error:</p>
  <pre class="lang-sql prettyprint-override"><code>SELECT 
      @Pro = CEILING((BaseDev * 100) / (ISNULL(BaseExe, 0) + ISNULL(BaseDev, 0)))
  FROM 
      (SELECT SUM(Base) 'BaseDev'
       FROM Table1
       WHERE Con = @Con AND Lib &lt;&gt; 0 AND Tip = 1 
         AND Fac = 'V' AND ISNULL(Pct, 0) &lt;&gt; 0) A,
      (SELECT SUM(Base) 'BaseExe'
       FROM Table1
       WHERE Con = @Con AND Lib &lt;&gt; 0 AND Tip = 1 AND Fac = 'V' 
         AND ISNULL(Pct, 0) = 0) B
  </code></pre>