title: Google Sheets' QUERY multiple sheets and return unique values
body: <p>I need to query two sheets and return all columns and unique values which match specific criteria.</p>
  
  <p>I've used this but it doesn't work:</p>
  
  <pre><code>=UNIQUE(QUERY(Sheet1!A:D,Sheet2!A:D, "select * where B=0"))
  </code></pre>
  
  <p>My shared sheet:</p>
  
  <p><a href="https://docs.google.com/spreadsheets/d/1ysuvyBHU21uXv_DxzBJwC7tMnGPyaqFqab7m1d-vwyo/edit?usp=sharing" rel="nofollow noreferrer">https://docs.google.com/spreadsheets/d/1ysuvyBHU21uXv_DxzBJwC7tMnGPyaqFqab7m1d-vwyo/edit?usp=sharing</a></p>