SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 4)
   ExpressionList (children 1)
    Asterisk
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 2)
      TableIdentifier tab
      SampleRatio 1 / 2
   ExpressionList (children 1)
    OrderByElement (children 1)
     Identifier x
   Literal UInt64_5