SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 1)
    Function count (children 1)
     ExpressionList
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier system.one
   Function less (children 1)
    ExpressionList (children 2)
     Function rand (children 1)
      ExpressionList
     Literal UInt64_0
