Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 2)
     Function max (children 1)
      ExpressionList (children 1)
       Identifier x1
     Identifier x2
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier test
    ExpressionList (children 1)
     Literal UInt64_2
    ExpressionList (children 2)
     OrderByElement (children 1)
      Literal UInt64_1
     OrderByElement (children 1)
      Literal UInt64_2