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 if (alias x) (children 1)
            ExpressionList (children 3)
             Function toUInt8 (children 1)
              ExpressionList (children 1)
               Literal UInt64_1
             Function toNullable (children 1)
              ExpressionList (children 1)
               Function toUInt8 (children 1)
                ExpressionList (children 1)
                 Literal UInt64_0
             Literal NULL