title: Change variable type during runtime
body: <p>Is it possible to change a variable type in SQL Server? Something like when you have</p>
  
  <pre><code>DECLARE @a INT;
  SET @a = 3
  </code></pre>
  
  <p>but later you want to use <code>@a</code> to store <code>VARCHAR</code>? Is there a way to undeclare it, change the data type it can store? Does T-SQL allow this?</p>