Here's your command: <code>UPDATE activity_overview SET 'D3' = 1 FROM activity_overview INNER JOIN query_projects ON activity_overview."Project ID"= query_projects."Project ID" WHERE activity_overview."Early Start" < query_projects."Planned Start"</code> Here's the error message: <code>Error: ambiguous column name: activity_overview.Early Start</code> So look at your SQLite command and search for things that might define <code>activity_overview.Early Start</code>. And there are indeed two of them. You use the table name <code>activity_overview</code> twice. Once immediately after the <code>UPDATE</code> keyword, and again after <code>FROM</code>. When you refer to <code>activity_overview</code> SQLite doesn't know whether to use the current row of the <code>UPDATE</code> command or the current row from the <code>INNER JOIN</code>. One way to fix this would be to use a table alias for one of them. For instance <code>UPDATE activity_overview AS activity_update …</code>