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convert varchar -> datetime with <nulls> and dd/mm/yyyy 00:00:00 in field [out-of-range error]

Hi,

I have 40,000 records which I want to to convert the date of birth field.

the field has about 50% of <NULL> and the rest have dates.

The dates are in the format for example 04/05/1977 0:00:00

I can remove the 0:00:00 because it is not relevant. (Is there an SQL command I can use to remove all of these?)

Is the NULL or the time causing the out-of-range error and is there any way around this?

I need to convert it to add more date records and dates not varchars in the future.

Regards,
tp
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tippingpoint
Asked:
tippingpoint
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1 Solution
 
jdlambert1Commented:
If you want to strip the 0:00:00 out of an existing varchar column this will do it:

UPDATE TableA SET ColA = Replace(ColA, ' 0:00:00','')

If you have date values in a varchar column and convert the column to a datetime data type, it will be stored as a number. If no time is specified the number will always be equal to 12 AM of the date.

If you want us to help you figure out what's causing the error, you need to post the query/command you're executing to generate the error.
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arbertCommented:
You need to look at the nulls before you attemp the conversion.  If your varchar "date" is always in MM/DD/YYYY then this will select the dates using left (you can build an update statement out of it as well):


SELECT CASE WHEN yourdobfield IS NULL THEN NULL
       ELSE CONVERT(DATETIME,LEFT(yourdobfield,10)) END
FROM yourinputtable
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tippingpointAuthor Commented:
arbert:
This is the error I got.

Server: Msg 242, Level 16, State 3, Line 1
The conversion of a char data type to a datetime data type resulted in an out-of-range datetime value.
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tippingpointAuthor Commented:
jdlambert1:
I have removed the times but it seems the <NULLS> in that column are not allowing me to convert it to datetime

Any other suggestions?
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arbertCommented:
So I take it you must also have some invalid dates in the column???

select
case when isdate(left(yourdobfield,10)) then CONVERT(DATETIME,LEFT(yourdobfield,10))
else null END
from yourinputtable
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arbertCommented:
Actually, sorry I didn't ask this earlier, what's the existing format of the field that contains DOB?  If there happen to be spaces at the beginning of the string, the would need to be stripped off with LTRIM.
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tippingpointAuthor Commented:
arbert:
Server: Msg 156, Level 15, State 1, Line 1
Incorrect syntax near the keyword 'then'.

still no good, do you think there are bad entries in there?
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tippingpointAuthor Commented:
it was a varchar,

I have removed spaces
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arbertCommented:
Sorry--I tested the first one and changed it without testing the second:

select case isdate(dobfield)
        when 1 then  CONVERT(DATETIME,LEFT(dobfield,10))
            else null END
from yourtable
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tippingpointAuthor Commented:
If there are invalid date entries in there is there a way to check if they are invalid and make them null??

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arbertCommented:
That's what the above does--if ISDATE is 0 then the date is invalid and it will return NULL.  If it's 1, it performs the conversion.
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tippingpointAuthor Commented:
It seems as though the above works, but it is converting my dates wrong using LEFT

my format is DD/MM/YYYY

it is being converted to YYYY-MM-DD which is ok but it is swicthing the DD and MM around in the output

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arbertCommented:
Sorry--dumb american here :)

add a 103 to the convert:

select case isdate(dob)
when 1 then  CONVERT(DATETIME,LEFT(dob,10),103)
else null END
from #datetest


The YYYY-MM-DD returned is just the iso representation of the date....
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tippingpointAuthor Commented:
ok all good!! :)

last thing..how do i update into that data table with that query... sorry i fairly new to sql!
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arbertCommented:
Well, I would either add a new column with a smalldate time definition, or you could update the existing data in-place and then change the column definition afterwards.

Update existing:

update your table
set dob= case isdate(dob)
when 1 then  CONVERT(DATETIME,LEFT(dob,10),103)
else null END


If you add a new column, just substitute the "set dob=" to be "set younewcolumn="

Brett


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arbertCommented:
Did you get it tp?
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tippingpointAuthor Commented:
VERY GOOD..

THANK YOU SO MUCH.

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