SQL WHERE DateTime is Between - sql

Question

I have this query here:
SELECT *
FROM QuestionnaireAnswer
WHERE dateCreated BETWEEN CAST('20/12/2015' AS datetime) AND CAST('22/12/2015' AS datetime)
but I keep getting this error, how come? and how do I fix it?
The conversion of a varchar data type to a datetime data type resulted in an out-of-range value.

Answer 1

There are many formats supported by SQL Server - see the MSDN Books Online on CAST and CONVERT. Most of those formats are dependent on what settings you have - therefore, these settings might work some times - and sometimes not.
The way to solve this is to use the (slightly adapted) ISO-8601 date format that is supported by SQL Server - this format works always - regardless of your SQL Server language and dateformat settings.
The ISO-8601 format is supported by SQL Server comes in two flavors:
YYYYMMDD for just dates (no time portion); note here: no dashes!, that's very important! YYYY-MM-DD is NOT independent of the dateformat settings in your SQL Server and will NOT work in all situations!
or:
YYYY-MM-DDTHH:MM:SS for dates and times - note here: this format has dashes (but they can be omitted), and a fixed T as delimiter between the date and time portion of your DATETIME.
This is valid for SQL Server 2000 and newer. In your concrete case, use this WHERE clause:
WHERE dateCreated BETWEEN '20151220' AND '20151222'
and you don't even need any explicit CAST operations (or if you want to use an explicit CAST - then I'd suggest you cast to a DATE datatype - rather than DATETIME).
If you use SQL Server 2008 or newer and the DATE datatype (only DATE - not DATETIME!), then you can indeed also use the YYYY-MM-DD format and that will work, too, with any settings in your SQL Server.
Don't ask me why this whole topic is so tricky and somewhat confusing - that's just the way it is. But with the YYYYMMDD format, you should be fine for any version of SQL Server and for any language and dateformat setting in your SQL Server.
The recommendation for SQL Server 2008 and newer is to use DATE if you only need the date portion, and DATETIME2(n) when you need both date and time. You should try to start phasing out the DATETIME datatype if ever possible

Answer 2

As a general rule when comparing dates in SQL Server don't use a format specific to a locale, use the universal ISO 8601 format 'yyyy/MM/dd' so the query becomes:
SELECT *
FROM QuestionnaireAnswer
WHERE dateCreated BETWEEN CAST('2015/12/20' AS datetime) AND CAST('2015/12/22' AS datetime)
You could also use one that is specific to a locale but you would have to ensure that the date format on the server always remains the same across all servers your code will connect to.

Answer 3

Using CONVERT you can write something like that:
SELECT *
FROM QuestionnaireAnswer
WHERE
dateCreated BETWEEN CONVERT(datetime, '20/12/2015', 103)
AND CONVERT(datetime, '22/12/2015', 103);

Answer 4

Check the locale settings on your server. My bet is that you are set for a US date format, but the date you have there is not in a US format.
More on querying the locale settings here.
This SO question has numerous ways to adjust the locale settings for SQL, including by user.
If you don't have permissions to change the locale for the whole server, you can change your locale within a session here. Note that SET LANGUAGE automatically sets the DATEFORMAT , but you can set the DATEFORMAT by itself.
To test this, try reversing the date and month in your date. Like so:
SELECT *
FROM QuestionnaireAnswer
WHERE dateCreated BETWEEN CAST('12/20/2015' AS datetime) AND CAST('12/22/2015' AS datetime)
Or try putting the date in a "locale insensitive format" like yyyymmdd HH:mm:ss.fff .

Answer 5

If column is a date field then you should do this:
SELECT *
FROM QuestionnaireAnswer
WHERE dateCreated BETWEEN TO_DATE('20-DEC-2015') AND TO_DATE('22-DEC-2015')
May not be 100% accurate depending on architecture and configuration.