Which is the best way to query data between 2 dates

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Which is the best way to query data between 2 dates

hnkumar

Old Hand

Points: 327
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June 26, 2012 at 7:12 am

#258468

Hi,
I'm facing a strange problem. We have 2 queries to fetch data between dates. However both queries are giving different values. First query is giving 8987 records but second query is giving only 8972 records. When we actually compare and we found that few records (18th June 2012 7:22AM) are missing in 2nd query.
Query1 - select count(*) from NONMEMBER_TRANS WHERE cast(convert(varchar(10),[Uploaded Date],101) as datetime) BETWEEN '2012-06-18' AND '2012-06-24'
Query2 - select count(*) from NONMEMBER_TRANS where convert(datetime, convert(char(10), [Uploaded Date], 103), 103) between convert(datetime, '18/06/2012', 103) and convert(datetime, '24/06/2012', 103)
When I'd a discussion with vendor and he is explaining that query2 is best and whatever record counts give that is valid. But when i actually check data then Query1 results are right.
Can you please help me here and understand which is one is best way to use and any guess on why records are missing in 2nd query.
Regards,
hnkumar

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Sean Lange SSC Guru Points: 286590 More actions · Answer 1

Hard to say with absolute certainty without seeing the ddl. Is this column a datetime datatype? If so you should not do any conversions at all.

The 2nd is just flat out wrong. It is converting a datetime to a string and then comparing the strings.

Assuming Uploaded Date is a datetime then a simple comparison is the best way.

[Uploaded Date] BETWEEN '2012-06-18' AND '2012-06-24'

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ChrisM@Work SSC Guru Points: 186127 More actions · Answer 2

hnkumar (6/26/2012)
Hi,
I'm facing a strange problem. We have 2 queries to fetch data between dates. However both queries are giving different values. First query is giving 8987 records but second query is giving only 8972 records. When we actually compare and we found that few records (18th June 2012 7:22AM) are missing in 2nd query.
Query1 - select count(*) from NONMEMBER_TRANS WHERE cast(convert(varchar(10),[Uploaded Date],101) as datetime) BETWEEN '2012-06-18' AND '2012-06-24'
Query2 - select count(*) from NONMEMBER_TRANS where convert(datetime, convert(char(10), [Uploaded Date], 103), 103) between convert(datetime, '18/06/2012', 103) and convert(datetime, '24/06/2012', 103)
When I'd a discussion with vendor and he is explaining that query2 is best and whatever record counts give that is valid. But when i actually check data then Query1 results are right.
Can you please help me here and understand which is one is best way to use and any guess on why records are missing in 2nd query.
Regards,
hnkumar

Your vendor is wrong - both queries are poor.

Find out which dates are missing:

SELECT

[Uploaded Date],

x.ConvertedDate,

x.RangeStart,

x.RangeEnd

FROM NONMEMBER_TRANS

CROSS APPLY (

SELECT

ConvertedDate = cast(convert(varchar(10),[Uploaded Date],101) as datetime),

RangeStart = CAST('2012-06-18' AS DATETIME),

RangeEnd = CAST('2012-06-24' AS DATETIME)

) x

WHERE x.ConvertedDate BETWEEN x.RangeStart AND x.RangeEnd

GROUP BY [Uploaded Date], x.ConvertedDate, x.RangeStart, x.RangeEnd

SELECT

[Uploaded Date],

ConvertedDate = convert(datetime, convert(char(10), [Uploaded Date], 103), 103),

RangeStart = convert(datetime, '18/06/2012', 103),

RangeEnd = convert(datetime, '24/06/2012', 103)

FROM NONMEMBER_TRANS

CROSS APPLY (

SELECT

ConvertedDate = convert(datetime, convert(char(10), [Uploaded Date], 103), 103),

RangeStart = convert(datetime, '18/06/2012', 103),

RangeEnd = convert(datetime, '24/06/2012', 103)

) x

WHERE x.ConvertedDate BETWEEN x.RangeStart AND x.RangeEnd

GROUP BY [Uploaded Date], x.ConvertedDate, x.RangeStart, x.RangeEnd

Then Google "SARGable". Whichever query is returning the correct results should be adjusted so that the date filter is SARGable.

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Lynn Pettis SSC Guru Points: 442467 More actions · Answer 3

I'd say both queries have issues as well. Since you are apparently using SQL Server 2005 (this is a SQL Server 2005 forum you posted in) and are using the DATETIME data type, there is the possibility that your dates could have a time portion other than 00:00:00.000. Even if you are 100% certain that this is not possible, when working with the DATETIME data time (or SMALLDATETIME), you should consider the possibility.

The best way to query a range of dates is to use a closed end comparision on the low end and an open end comparision on the high end. Using the first query:

select count(*) from NONMEMBER_TRANS WHERE cast(convert(varchar(10),[Uploaded Date],101) as datetime) BETWEEN '2012-06-18' AND '2012-06-24'

it should look like this:

select count(*) from NONMEMBER_TRANS WHERE [Uploaded Date] >= '20120618' AND [Uploaded Date] < '20120625';

You will also note I took the hyphens out of the dates, and adjusted the upper date from 20120624 to 20120625. With the hyphens, this query would also fail if the DATEFORMAT were set to DMY.

Jeff Moden SSC Guru Points: 1004406 More actions · Answer 4

Lynn Pettis (6/26/2012)
I'd say both queries have issues as well. Since you are apparently using SQL Server 2005 (this is a SQL Server 2005 forum you posted in) and are using the DATETIME data type, there is the possibility that your dates could have a time portion other than 00:00:00.000. Even if you are 100% certain that this is not possible, when working with the DATETIME data time (or SMALLDATETIME), you should consider the possibility.
The best way to query a range of dates is to use a closed end comparision on the low end and an open end comparision on the high end. Using the first query:
select count(*) from NONMEMBER_TRANS WHERE cast(convert(varchar(10),[Uploaded Date],101) as datetime) BETWEEN '2012-06-18' AND '2012-06-24'
it should look like this:
select count(*) from NONMEMBER_TRANS WHERE [Uploaded Date] >= '20120618' AND [Uploaded Date] < '20120625';
You will also note I took the hyphens out of the dates, and adjusted the upper date from 20120624 to 20120625. With the hyphens, this query would also fail if the DATEFORMAT were set to DMY.

+1

I think that any use of CONVERT to filter dates is just begging for an SQL nose bleed just like the one that happened in the original post.

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