Converting string to datetime in yyyymmdd format - sql-server

Question

I need to add days to a varchar representation in the yyyymmdd format.
I'm getting an error when converting a varchar(8) value to datetime in SQL Server 2005.
I don't have a clue why!
Here is what works:
select
convert (datetime, '20111019')
from _table
This does not work, although the value in the column is 20111019
select
convert (datetime, RechDatum)
from _table
I already tried:
convert (datetime, RechDatum, 112)
and
SET DATEFORMAT ymd
I was able to solve the problem with an own function. But I'm still confused and would be glad for answers of you!
IF EXISTS (SELECT * FROM sysobjects WHERE name = 'getDateFromString' and type = 'FN')
DROP FUNCTION getDateFromString
GO
CREATE FUNCTION getDateFromString (#Cyear VARCHAR(4), #Cmonth smallint, #Cday smallint, #offsetdays smallint)
RETURNS DATETIME
AS BEGIN
DECLARE #day SMALLINT
DECLARE #month SMALLINT
DECLARE #year SMALLINT
SET #day = CAST (#Cday AS SMALLINT)
SET #month = CAST (#Cmonth AS SMALLINT)
SET #year = CAST (#Cyear AS SMALLINT)
RETURN DateAdd(day, #offsetdays,
(SELECT
DateAdd (day, #day -1,
DateAdd (month, #month -1,
DateAdd (Year, #year-1900,0))) ))
END
GO
Here is the table definition, it's part of an german ERP system:
CREATE TABLE [dbo].[AuftrKopf](
[ID] [int] IDENTITY(1,1) NOT NULL,
[IsSammelRechnung] [bit] NULL,
[AuftragsNr] [int] NULL,
[Kd_ID] [int] NULL,
[Fahrer_ID] [int] NULL,
[Debitor] [int] NULL,
[Fz_ID] [int] NULL,
[FHFz_ID] [int] NULL,
[AuftrArt_ID] [int] NULL,
[AuftrHerkunft_ID] [int] NULL,
[AuftrZustand_ID] [int] NULL,
[RechnungsArt_ID] [int] NULL,
[AuftragVom] [varchar](8) NULL,
[FertigAmUm] [varchar](12) NULL,
[BringenAmUm] [varchar](12) NULL,
[AbgeschlossenAmUm] [varchar](12) NULL,
[StempelkartenNr] [int] NULL,
[HuetchenNr] [int] NULL,
[LeistungsDatum] [varchar](8) NULL,
[RechnDatum] [varchar](8) NULL,
[ValutaDatum] [varchar](8) NULL,
[NettoSummenspalte1] [decimal](18, 2) NULL,
[NettoSummenspalte2] [decimal](18, 2) NULL,
[NettoSummenspalte3] [decimal](18, 2) NULL,
[NettoSummenspalte4] [decimal](18, 2) NULL,
[NettoSummenspalte5] [decimal](18, 2) NULL,
[NettoSummenspalte6] [decimal](18, 2) NULL,
[NettoSummenspalte7] [decimal](18, 2) NULL,
[NettoSummenspalte8] [decimal](18, 2) NULL,
[NettoSummenspalte9] [decimal](18, 2) NULL,
[NettoSummenspalte10] [decimal](18, 2) NULL,
[NettoOhneSummenSpalte] [decimal](18, 2) NULL,
[MwStSummenspalte1] [decimal](18, 2) NULL,
[MwStSummenspalte2] [decimal](18, 2) NULL,
[MwStSummenspalte3] [decimal](18, 2) NULL,
[MwStBasisspalte1] [decimal](18, 2) NULL,
[MwStBasisspalte2] [decimal](18, 2) NULL,
[MwStBasisspalte3] [decimal](18, 2) NULL,
[BasisspalteOhneMwSt] [decimal](18, 2) NULL,
[KdNr] [int] NULL,
[KdNachname] [nvarchar](50) NULL,
[KdVorname] [nvarchar](50) NULL,
[KdTelefon] [nvarchar](30) NULL,
[KdMobilTelefon] [nvarchar](30) NULL,
[KdEmail] [nvarchar](100) NULL,
[Kennz] [nvarchar](20) NULL,
[BerKennz] [nvarchar](20) NULL,
[KM] [int] NULL,
[Laufleistung] [int] NULL,
[RabattStufe] [int] NULL,
[Adresse_ID] [int] NULL,
[CPrLieferschein] [int] NULL,
[BincMwSt] [bit] NULL,
[LandWKuerzel] [nvarchar](4) NULL,
[Bemerkung] [nvarchar](50) NULL,
[Verkaeufer_ID] [int] NULL,
[Sachbearbeiter_ID] [int] NULL,
[PersIDFaktura] [int] NULL,
[Monteur_ID] [int] NULL,
[Team_ID] [int] NULL,
[CPrRepAngebot] [int] NULL,
[CPrRepAuftr] [int] NULL,
[CPrWerkstattkarte] [int] NULL,
[CPrRechnung] [int] NULL,
[CPrRechnungFormularName] [nvarchar](50) NULL,
[CPrRepRechnKopie] [int] NULL,
[CPrPickerzettel] [int] NULL,
[CPrVorabRechn] [int] NULL,
[CPrAuftrBestaet] [int] NULL,
[BOhneFzDaten] [bit] NULL,
[BOhneNr] [bit] NULL,
[PrOhneEinzelpreis] [bit] NULL,
[FHFzNW] [bit] NULL,
[FHDifferenzbesteuert] [bit] NULL,
[StornoZuAuftrNr] [int] NULL,
[Storno_Datum] [varchar](8) NULL,
[Buchungsdatum] [varchar](14) NULL,
[VakBuchungsModus] [int] NULL,
[DiffNettoKompZuSumme] [decimal](18, 2) NULL,
[Vorgangsart_ID] [int] NULL,
[Beschreibung] [ntext] NULL,
[IsErreichbarTel1perSMS] [bit] NULL,
[IsErreichbarTel1perTel] [bit] NULL,
[IsErreichbarMobilperSMS] [bit] NULL,
[IsErreichbarMobilperTel] [bit] NULL,
[IsErreichbarEmail] [bit] NULL,
[StundenGeschaetzt] [decimal](18, 2) NULL,
[WKZ_Zweitwaehrung] [nvarchar](3) NULL,
[Kurs_Zweitwaehrung] [decimal](18, 7) NULL,
[EndbetragInZweitwaehrung] [bit] NULL,
[Kulanzursprung] [int] NULL,
[IsKulanzgesplittet] [bit] NULL,
[SplitUrsprung] [int] NULL,
[IsGesplittet] [bit] NULL,
[FlottenReparaturkostenId] [int] NULL,
[NovaSatz] [decimal](18, 2) NULL,
[NovaGesamt] [decimal](18, 2) NULL,
[NovaBasis] [decimal](18, 2) NULL,
[NovaBonusMalus] [decimal](18, 2) NULL,
[FilialNr] [int] NULL,
[Angebotverfall] [varchar](8) NULL,
[IvecoSonderverkauf] [bit] NULL,
[LetzteAenderung] [varchar](14) NULL,
[IsAnzahlung] [bit] NULL,
[AnzahlungSumme] [decimal](18, 2) NULL,
[SADESperre] [int] NULL,
[SADEVersendet] [varchar](14) NULL,
[MP2Angebotsnummer] [int] NULL,
[SchadenNummer] [nvarchar](20) NULL,
[ReferenzAudaNet] [nvarchar](40) NULL,
[LetzterBearbeiter] [nvarchar](50) NULL,
[Rechnername] [nvarchar](50) NULL,
[ReferenzAudaNetCaseId] [nvarchar](40) NULL,
[AuftragsanlageOrder] [bit] NULL,
[RabattDrucken] [bit] NULL,
[AuftragStatus1_ID] [int] NULL,
[AuftragStatus2_ID] [int] NULL,
[AuftragStatus3_ID] [int] NULL,
[AuftragStatus4_ID] [int] NULL,
[TeileZurueckBeiGutschrift] [bit] NULL,
[StornoGrund_ID] [int] NULL,
[Anleger_ID] [int] NULL,
[Betriebsstunden] [int] NULL,
[SperreSADE] [bit] NULL,
[FiOnlineContractId] [nvarchar](20) NULL,
[DWNichtMehrFragen] [bit] NULL,
[BestellZaehler] [int] NULL,
[NovaOhneAufschlag] [bit] NULL,
[DefaultLager_ID] [int] NULL,
[RechnungBezahltKennzeichnen] [bit] NULL,
[AnVWBackboneAsNewReported] [bit] NULL,
[VWBackboneRequestID] [nvarchar](20) NULL,
[VWBackboneConversationID] [nvarchar](70) NULL,
[VWBackboneStatusID] [int] NULL,
[VWBackboneSaga2ClaimNr] [nvarchar](2) NULL,
[VWBackboneSaga2GarantieAntragNr] [int] NULL,
[VWBackboneSaga2MaxClaims] [int] NULL,
CONSTRAINT [PK_AuftrKopf] PRIMARY KEY CLUSTERED
(
[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO
The strange thing is, that the conversions work on my computer with german-swiss settings, but not on the client-computer, which has a french setup.

Answer 1

This works:
DECLARE #datevar varchar(8)
SET #datevar = '20111019'
SELECT CONVERT(DATETIME,#datevar,114) AS RechDatum
And this:
SELECT '20111019' AS RechDatum INTO #tmp
SELECT CONVERT(DATETIME,Rechdatum,114) AS RechDate from #tmp
works fine too. Are you sure you table column has the right type/format?

Answer 2

I found the solution to the problem with the input of Laszlo Tenki.
I read the SET DATEFORMAT-article of the Microsoft Help again:
http://msdn.microsoft.com/en-us/library/ms189491.aspx
It seems that there are some character string formats, that are independent of SET DATEFORMAT.
From the Microsoft-Article:
Some character strings formats, for example ISO 8601, are interpreted independently of the DATEFORMAT setting. For more information about how to use DATEFORMAT with different formats see the "String Literal Date and Time Formats" section in Using Date and Time Data.
The solution answer can be found here:
http://msdn.microsoft.com/en-us/library/ms180878.aspx
I could solve the problem with
SET LANGUAGE
Set language sets the SQL-Server-Settings for the Current Session.
The interpretation of String representations by the SQL-Server is dependent on SET DATEFORMAT and SET LANGUAGE.
The format I chose ISO 8601 is 'SET DATETIME'-independent, thats why that didn't work.
Check the info here:
http://msdn.microsoft.com/en-us/library/ms180878.aspx
However: Microsoft recommends the usage of ISO 8601, because it is multilanguage-compatible. That raises the question, why I needed to change the LANGUAGE at all.

Answer 3

SQL server has its own date formatting mechanism that is independent from the regional settings of the computer.
I would say that it is probably different on your developer machine and the production server. It looks that you can process dates in either format, your only problem is that it changes and you don't know for sure what to prepare for.
For SET DATEFORMAT, See the details here:
http://msdn.microsoft.com/en-us/library/ms189491.aspx