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 isNull (children 1)
        ExpressionList (children 1)
         Literal UInt64_1
       Literal \'Int32\'