SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function if (children 1)
     ExpressionList (children 3)
      Literal UInt64_1
      Function toLowCardinality (children 1)
       ExpressionList (children 1)
        Literal \'a\'
      Literal \'b\'
