SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function if (children 1)
     ExpressionList (children 3)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier xxx
        Literal \'x\'
      Function tuple (children 1)
       ExpressionList (children 2)
        Literal Array_[UInt64_2]
        Literal UInt64_3
      Function tuple (children 1)
       ExpressionList (children 2)
        Literal Array_[UInt64_3]
        Literal UInt64_4
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier agg_table