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 x
        Literal UInt64_0
      Literal \'ok\'
      Literal \'fail\'
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Subquery (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 1)
          ExpressionList (children 1)
           Function toNullable (alias x) (children 1)
            ExpressionList (children 1)
             Function toUInt8 (children 1)
              ExpressionList (children 1)
               Literal UInt64_0