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Why is the T-SQL "DATEPART" Not Working?

Hello:

I'm running a simple select statement against a SQL Server 2008 R2 database, as follows:

select * from RM20101 where RMDTYPAL = 7 and DATEPART(y, RM20101.DOCDATE) < '2011'

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The RM20101 table is a list of accounts receivable (i.e. "sales") documents.  The syntax " where RMDTYPAL = 7" means to only return a list of credit memos.  Finally, the "DATEPART" syntax is to return credit memos only where the year portion of the document's date is older than the year 2011.

But, if you look at the image that I have embedded, this statement is returning documents dated with the year 2013.

What am I doing wrong?

DOCDATE
Thank you!

John
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John Ellis
Asked:
John Ellis
1 Solution
 
Éric MoreauSenior .Net ConsultantCommented:
because y is dayofyear. you need to use yy or yyyy as shown in https://msdn.microsoft.com/en-us/library/ms174420.aspx
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PortletPaulfreelancerCommented:
I have no idea how many rows you have in that table, but for every row you are running a function
e.g. 100,000 rows = 100,000 function executions

Or, you could do this instead which leads to zero function executions

and RM20101.DOCDATE < '20110101' -- i.e. less than Jan 1 2011


"avoid using functions on data in the where clause"
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