title: "Ambiguous column name" when joining tables
body: <p>I'm having difficulty in pulling the userID from joining these two tables. </p>
  
  <p>My goal is to find all vacation balance over 200 and all active userID but I keep getting an ambiguous column name for userID. </p>
  
  <p>My query does work if i try to pull anything else, but I want to pull UserID instead. Any help on my query will be appreciated. </p>
  
  <p><strong>Here is my table and its columns:</strong> <br><br>
  Table <strong>USER</strong></p>
  
  <pre><code>ID (PK)
  UserID
  Firstname
  Lastname
  Email
  Active (Bool) 
  </code></pre>
  
  <p>Table <strong>Balance</strong></p>
  
  <pre><code>UserID (PK)
  VacationBalance
  </code></pre>
  
  <p><strong>Here is my Query:</strong></p>
  
  <pre><code>SELECT UserID FROM dbo.VacBal as I join dbo.User as T
  on I.userid = T.userid 
  WHERE VacationBalance &gt; 200 and active = 1 
  </code></pre>
  
  <p><strong>Here is the error I'm getting:</strong></p>
  
  <blockquote>
    <p>Msg 209, Level 16, State 1, Line 1 Ambiguous column name 'userid'.</p>
  </blockquote>