Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 1)
    ExpressionList (children 1)
     Function CAST (children 1)
      ExpressionList (children 2)
       Function array (children 1)
        ExpressionList (children 2)
         Function CAST (children 1)
          ExpressionList (children 2)
           Function array (children 1)
            ExpressionList (children 2)
             Function CAST (children 1)
              ExpressionList (children 2)
               Literal \'1\'
               Literal \'UInt16\'
             Function CAST (children 1)
              ExpressionList (children 2)
               Literal \'2\'
               Literal \'UInt16\'
           Literal \'Array(UInt32)\'
         Literal Array_[UInt64_3]
       Literal \'Array(Array(UInt64))\'
