SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function isNull (children 1)
     ExpressionList (children 1)
      Identifier nullableStringCol
   TablesInSelectQuery (children 3)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier users_ext
    TablesInSelectQueryElement (children 2)
     TableExpression (children 1)
      TableIdentifier users (alias users2)
     TableJoin (children 1)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier users_ext.uid
        Identifier users2.uid
    TablesInSelectQueryElement (children 2)
     TableExpression (children 1)
      TableIdentifier users
     TableJoin (children 1)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier users2.uid
        Identifier users.uid
