SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function mapFromArrays (children 1)
     ExpressionList (children 2)
      Function array (children 1)
       ExpressionList (children 2)
        Function toLowCardinality (children 1)
         ExpressionList (children 1)
          Function toNullable (children 1)
           ExpressionList (children 1)
            Literal \'x\'
        Function toLowCardinality (children 1)
         ExpressionList (children 1)
          Function CAST (children 1)
           ExpressionList (children 2)
            Literal NULL
            Literal \'Nullable(String)\'
      Literal Array_[UInt64_3, UInt64_4]
   ExpressionList (children 1)
    Literal UInt64_1
