Comments on: Dates can easily be the hardest datatype to work with.

By: mrdenny

mrdenny — Thu, 24 Sep 2009 19:46:37 +0000

You should be able to do something like this without two much overhead.

WHERE tab1.col1 BETWEEN CAST(convert(varchar(10, tab2.col1, 101) as datetime) and dateadd(ms, -3, dateadd(dd, 1, cast(convert(varchar(10), tab2.col1, 101) as datetime)))

Check my Parens, I think they are correct, but I’m not sure.

By: Sowmi

Sowmi — Wed, 23 Sep 2009 03:16:36 +0000

In my case i need to compare date portion alone from two different table’s datetime fields. I used convert in both sides of the comparision and this join itself resulting in 53 % of the overall cost of the query and results in performance degration. How to tune this query and can we use a syntax similar to this
tab1.col1 between tab2.col1 and tab2.col1. Please advise asap. thanks a lot.

By: mrdenny

mrdenny — Thu, 17 Sep 2009 23:22:39 +0000

This is true, BETWEEN is inclusive, so to use BETWEEN correctly you’d want to use

WHERE dt BETWEEN ‘01/01/2000′ AND dateadd(ms, -3, ‘01/02/2000′)

Unless you were using SQL 2008’s new data types

WHERE dt BETWEEN ‘01/01/2000′ AND dateadd(ns, -1, ‘01/02/2000′)

By: Gmmastros

Gmmastros — Thu, 17 Sep 2009 21:29:22 +0000

Sorry, that should have been:

WHERE dt >= ‘01/01/2000′ AND dt < ‘01/02/2000′

By: Gmmastros

Gmmastros — Thu, 17 Sep 2009 21:27:18 +0000

WHERE dt BETWEEN ‘01/01/2000′ AND ‘01/02/2000′

You need to be careful when using between and dates. That where clause will return rows from the table where the date is 01/02/2000 and the time is midnight. When working with dates, I prefer to use multiple conditions, like this…

WHERE dt >= ‘01/01/2000′ AND dt = for the start range and < for the end.

By: My Weekly Bookmarks for September 17th | Brent Ozar - SQL Server DBA

My Weekly Bookmarks for September 17th | Brent Ozar - SQL Server DBA — Thu, 17 Sep 2009 21:15:47 +0000

[...] Dates can easily be the hardest datatype to work with. – Good post by Denny Cherry about indexing date fields. [...]

By: BrianTkatch

BrianTkatch — Thu, 17 Sep 2009 13:08:04 +0000

Nice explanation and examples.

I’m bookmarking this one to help explain this concept to others.