ClickHouse Union All exception - clickhouse

Question

I wrote create view expression with union all.
create view if not exists V_REGRESULT as select 1 AS jType,
regF.smscid AS SmscID,
regF.eventdate AS EventDate,
regF.smppid AS SmppID,
regF.registereddate AS RegisteredDate,
regF.sendernpid AS SenderNPid,
regF.senderntid AS SenderNTid,
regF.senderdirectionid AS SenderDirectionID,
regF.CgPN AS CgPN,
regF.OriginalCgPn AS OriginalCgPN,
regF.recipientnpid AS RecipientNPid,
regF.recipientntid AS RecipientNTid,
regF.recipientdirectionid AS RecipientDirectionID,
regF.cdpn AS CdPN,
regF.OriginalCdPn AS OriginalCdPN,
regF.ValidityPeriod AS ValidityPeriod,
regF.expireddate AS ExpiredDate,
regF.deliveryreporttypeid AS DeliveryReportTypeID,
regF.umr AS Umr,
regF.smtypeid AS SmTypeID,
regF.uhdiheaderinsm AS UhdiHeaderInsm,
regF.uhdisequenceid AS UhdiSequenceID,
regF.uhdipartstotal AS UhdiPartsTotal,
regF.uhdipartn AS UhdiPartN,
regF.setbackpath AS SetBackPath,
regF.smppencoding AS SmppEncoding,
regF.originalsmppencoding AS OriginalSmppEncoding,
regF.retrycount AS RetryCount,
regF.retrycountsh AS RetryCountsH,
regF.schemeid AS SchemeID,
regF.lasterrortypeid AS LastErrorTypeID,
regF.lastneterror AS LastNetError,
regF.lastsmpperror AS LastSmppError,
regF.lastnativeerror AS LastNativeError,
regF.smstatusid AS SmStatusID,
regF.reportstatus AS ReportStatus,
regF.protocolid AS ProtocolID,
regF.modifiedprotocolid AS ModifiedProtocolID,
regF.dbencoding AS DbEncoding,
regF.messagelen AS MessageLen,
regF.smbody AS SmBody,
regF.senderserviceid AS SenderServiceID,
regF.recipientserviceid AS RecipientServiceID,
regF.imsi AS Imsi,
regF.commutatorgt AS CommutatorGT,
regF.targetimsi AS TargetImsi,
regF.targetcommutatorgt AS TargetCommutatorGT,
regF.eventflag AS EventFlag,
regF.failcode AS FailCode,
regF.ScpGt AS ScpGt,
regF.ResultCode AS ResultCode
from SMCS.V_REGFAIL regF
union all
select 2 AS jType,
reg.SmscId AS SmscID,
reg.EventDate AS EventDate,
reg.SmppID AS SmppID,
reg.RegisteredDate AS RegisteredDate,
reg.SenderNPID AS SenderNPid,
reg.SenderNTID AS SenderNTid,
reg.SenderDirectionID AS SenderDirectionID,
reg.CgPN AS CgPN,
reg.OriginalCgPN AS OriginalCgPN,
reg.RecipientNPid AS RecipientNPid,
reg.RecipientNTid AS RecipientNTid,
reg.RecipientDirectionID AS RecipientDirectionID,
reg.CdPN AS CdPN,
reg.OriginalCdPN AS OriginalCdPN,
reg.ValidityPeriod AS ValidityPeriod,
reg.ExpiredDate AS ExpiredDate,
reg.DeliveryReportTypeID AS DeliveryReportTypeID,
reg.Umr AS Umr,
reg.SmTypeID AS SmTypeID,
reg.UhdiHeaderInsm AS UhdiHeaderInsm,
reg.UhdiSequenceID AS UhdiSequenceID,
reg.UhdiPartsTotal AS UhdiPartsTotal,
reg.UhdiPartN AS UhdiPartN,
reg.SetBackPath AS SetBackPath,
reg.SmppEncoding AS SmppEncoding,
reg.OriginalSmppEncoding AS OriginalSmppEncoding,
reg.RetryCount AS RetryCount,
reg.RetryCountsH AS RetryCountsH,
reg.SchemeID AS SchemeID,
reg.LastErrorTypeID AS LastErrorTypeID,
reg.LastNetError AS LastNetError,
reg.LastSmppError AS LastSmppError,
reg.LastNativeError AS LastNativeError,
reg.SmStatusID AS SmStatusID,
reg.ReportStatus AS ReportStatus,
reg.ProtocolID AS ProtocolID,
reg.ModifiedProtocolID AS ModifiedProtocolID,
reg.DbEncoding AS DbEncoding,
reg.MessageLen AS MessageLen,
reg.SmBody AS SmBody,
reg.SenderServiceID AS SenderServiceID,
reg.RecipientServiceID AS RecipientServiceID,
reg.Imsi AS Imsi,
reg.CommutatorGT AS CommutatorGT,
reg.TargetImsi AS TargetImsi,
reg.TargetCommutatorGT AS TargetCommutatorGT,
'' AS EventFlag,
'' AS FailCode,
reg.ScpGt AS ScpGt,
'' AS ResultCode
from SMCS.V_REGISTRATION reg
;
All columns in requested views exists. I haven't got any idea about this exception
Code: 386, e.displayText() = DB::Exception: There is no supertype for types String, DateTime because some of them are String/FixedString and some of them are not (version 19.15.3.6 (official build))
Where could be there a mistake? Simple union like select 1 as one union all select 2 as one works good. The only thing i found was that error was caused due to Array Join, when type casting.
Initally, i was thinking that this was caused due to NULL casting at EventFlag, e.t.c, while union and replace NULL with ''. But nothing has changed
Help, pls
p.s. sorry for my english

Answer 1

select now() union all select ''
Code: 386. DB::Exception: Received from localhost:9000.
DB::Exception: There is no supertype for types DateTime, String
because some of them are String/FixedString and some of them are not.
cast to String
select toString(now()) union all select ''
┌─toString(now())─────┐
│ 2019-11-19 14:25:13 │
└─────────────────────┘
┌─toString(now())─┐
│ │
└─────────────────┘
'cast' to DateTime
select now() union all select toDateTime(0)
┌───────────────now()─┐
│ 2019-11-19 14:25:48 │
└─────────────────────┘
┌───────────────now()─┐
│ 0000-00-00 00:00:00 │
└─────────────────────┘