Comparision of a datetime variable against a column of the type nvarchar

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Comparision of a datetime variable against a column of the type nvarchar

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renu.iitkgp

Posted Sunday, September 02, 2012 11:27 PM

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Last Login: Wednesday, September 05, 2012 5:56 AM
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Hello All,

(Sorry, if I have posted this question already in another topic)

I have a table like this:

MinionRpt
(
Id [int], FullName [nvarchar](100), ..., EstDate [nvarchar](100)
)

If you noticed, the column [EstDate] (Estimated Date) is nvarchar(100). It need not always contain a date.

Now I gotta query like this:

select * from MinionRpt where DateDiff (d, EstDate, @StartDate) <= 0 and DateDiff(d, EstDate, @EndDate) >= 0

The problem is when we have invalid formats or gibberish for EstDate in some records, the query would throw an error.

I have no control over the existing data or any future data or even the schema design.

Can some one tell me, how I should go about it?

Thanks in advance,
Venkat R Prasad.

Post #1353340

dwain.c

Posted Sunday, September 02, 2012 11:54 PM

SSCrazy

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Last Login: Today @ 6:03 AM
Points: 2,345, Visits: 3,191

First of all, you need to gather your courage and tell your DBA that this design is complete crap and it must be changed. EstDate should be a DATETIME column and should never contain gibberish (you can put that in another column: GARBAGE VARCHAR(100)).

Of course, you won't do that, so you have two options:

1. Create a computed column for EstDate2 that is something like:

CASE WHEN [data is garbage] THEN GETDATE() ELSE EstDate END

2. Replace EstDate in your query with something like:

CASE WHEN [data is garbage] THEN @StartDate ELSE EstDate END

The [data is garbage] is some kind of test of the format to see whether it can be converted to a valid DATETIME value. Since you did not provide the format for the date, I can't tell you what that might be.

No loops! No CURSORs! No RBAR! Hoo-uh!

INDEXing a poor-performing query is like putting sugar on cat food. Yeah, it probably tastes better but are you sure you want to eat it?

Need to UNPIVOT? Why not CROSS APPLY VALUES instead?
Since random numbers are too important to be left to chance, let's generate some!
Are you too recursively challenged?
Splitting strings based on patterns can be fast!

Post #1353344

renu.iitkgp

Posted Monday, September 03, 2012 1:32 AM

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Last Login: Wednesday, September 05, 2012 5:56 AM
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Thank you Dwain, got that. My bad, I should've tried with:

CASE WHERE (BLADIDAA) THEN (TITUMTITUM) ELSE (DIDADIDAA) END

before I posted here.
Smile

Post #1353369

renu.iitkgp

Posted Tuesday, September 04, 2012 9:15 AM

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Group: General Forum Members
Last Login: Wednesday, September 05, 2012 5:56 AM
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Hi Dwain,

My query seemed to work on some server which runs SQL server 2000. When I execute the same on SQL Server 2008, I get the error: Conversion failed when converting date and/or time from character string.

My table is like this:

CRM_Request
(
Id [int] <PK, identity>,
TRNumber [nvarchar](50),
.....,
ExpectedCompletionDate [nvarchar](50),
UploadDate [nvarchar](50)
)

My actual query is this:

/*@DateSpec = 1 ---> fetch [ExpectedCompletionDate]; 2 ---> fetch [UploadDate] */

SELECT TRRpt.Id TRId, TRRpt.TRNumber, DateSpecified
FROM

(
select a.Id, a.TRNumber,

(
CASE WHEN @DateSpc = 1 THEN a.ExpectedCompletionDate
ELSE LTRIM(RTRIM(a.UploadDate)) END
) AS DateSpecified,

from CRM_Request a

where
(
(@DateSpc = 1 and IsDate(a.ExpectedCompletionDate) = 1)
or
(@DateSpc = 2 and IsDate(a.UploadDate) = 1)
)

) TRRpt

WHERE
DateDiff(d, TRRpt.DateSpecified, @StartDate) <= 0 and
DateDiff(d, TRRpt.DateSpecified, @EndDate) >= 0

If I remove the "where clause" the query throws results with the dates like

8/31/2011 5:27:44 PM
09/26/2011
08/28/2012
8/7/2007
06-09-2009
08/13/10
08/18/10
9/9/2010

As you can see, it has all possible datetime formats for strings.
Can you plz tell me what seems to be the problem?

Thanks in advance,
Venkat R Prasad.

Post #1353984

dwain.c

Posted Tuesday, September 04, 2012 6:38 PM

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Last Login: Today @ 6:03 AM
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ISDATE is sensitive to DATEFORMAT (Google "SQL DATEFORMAT"), so that could be your problem.

Personally I don't think I'd use it. Perhaps constructing a test (maybe a FUNCTION) for the validation might be more effective because it gives you better control.

This forum post may give you some additional ideas: http://www.sqlservercentral.com/Forums/Topic1178655-338-2.aspx#bm1183837

Post #1354287

renu.iitkgp

Posted Wednesday, September 05, 2012 6:03 AM

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Group: General Forum Members
Last Login: Wednesday, September 05, 2012 5:56 AM
Points: 12, Visits: 31

Thank you again Dwain. I already wrote a function which takes in a string and returns datetime. (returns 1/1/1900, if it's an invalid date format or gibberish.) That solved it. Smile

Post #1354456

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