SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 3)
    Function isNull (children 1)
     ExpressionList (children 1)
      Identifier t1.nullableStringCol
    Function isNull (children 1)
     ExpressionList (children 1)
      Identifier t2.nullableStringCol
    Function isNull (children 1)
     ExpressionList (children 1)
      Identifier t3.nullableStringCol
   TablesInSelectQuery (children 3)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier users_ext (alias t1)
    TablesInSelectQueryElement (children 2)
     TableExpression (children 1)
      TableIdentifier users_ext (alias t2)
     TableJoin (children 1)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier t1.uid
        Identifier t2.uid
    TablesInSelectQueryElement (children 2)
     TableExpression (children 1)
      TableIdentifier users_ext (alias t3)
     TableJoin (children 1)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier t1.uid
        Identifier t3.uid
