ROUND() function doesn't round properly

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ROUND() function doesn't round properly

ESB

Old Hand

Points: 364
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October 2, 2009 at 4:00 am

#139223

Hello. I use SQL Server 2005 and I'm calculating the age of patients in the following manner:
DATEDIFF(DAY, birthdate, operationdate)/365.25
The output always seems to be a decimal with 6 decimal digits. The rounding problem arises with border cases like for instance an age of 60.444445. If you round this properly it should result in 60.45 and that should result in 60.5. However, when I use [font="Courier New"]ROUND(60.444445, 1)[/font] it results in 60.4!
The problem is that SQL Server seems to ignore the digits after the rounding border. [font="Courier New"]ROUND(60.449999, 1)[/font] for instance also results in 60.4. It seems to truncate it 1 position behind the rounding index and starts rounding after that.
I found out that using the ROUND() function repeatedly in the following manner solves the issue but it is a bit ridiculous:
PRINT ROUND(ROUND(ROUND(ROUND(ROUND(60.444445, 5), 4), 3), 2), 1)
Is there any other way to solve this and am I missing something?
Thanks in advance!

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Dave Ballantyne SSC-Dedicated Points: 33667 More actions · Answer 1

Heres how to calculate an age

select CASE

WHEN dateadd(year, datediff (year, d1, d2), d1) > d2

THEN datediff (year, d1, d2) - 1

ELSE datediff (year, d1, d2)

END as Age

I'll take a look at the rounding issue though...

Clear Sky SQL
My Blog[/url]

Dave Ballantyne SSC-Dedicated Points: 33667 More actions · Answer 2

I think you are wrong in your assessment of round though,

round(60.444445,1) = 60.4

This

PRINT ROUND(ROUND(ROUND(ROUND(ROUND(60.444445, 5), 4), 3), 2), 1)

works because you are rounding a rounded , rounded, rounded , rounded number (ie the 5 has for want of a better word been cascaded up)

Clear Sky SQL
My Blog[/url]

ESB Old Hand Points: 364 More actions · Answer 3

For some reason that way of rounding was in my head. But I spoke with others about and I think SQL Server does round it correctly yes.

Jeff Moden SSC Guru Points: 1004329 More actions · Answer 4

Dave Ballantyne (10/2/2009)
Heres how to calculate an age
select CASE
WHEN dateadd(year, datediff (year, d1, d2), d1) > d2
THEN datediff (year, d1, d2) - 1
ELSE datediff (year, d1, d2)
END as Age
I'll take a look at the rounding issue though...

That's one of the simplest I've seen. Correctly handles the Feb 29 problem that most other's don't handle, too!

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

Dave Ballantyne SSC-Dedicated Points: 33667 More actions · Answer 5

Cant take the credit for it ...

http://windowsitpro.com/article/articleid/14267/how-can-i-calculate-someones-age-in-sql-server.html

Clear Sky SQL
My Blog[/url]

Jeff Moden SSC Guru Points: 1004329 More actions · Answer 6

Shoot... the link is broken. Thanks anyway, Dave.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

Dave Ballantyne SSC-Dedicated Points: 33667 More actions · Answer 7

Seems fine now, just a temporary thing i guess.

TBH , its hardly worth the click though 🙂 simple Q and A

Clear Sky SQL
My Blog[/url]

Jeff Moden SSC Guru Points: 1004329 More actions · Answer 8

Hmmmm.... something must be wrong on my end. It keeps giving me a 404 error.

Q & A's are sometimes pretty rich in information like the little date jewel you found.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

hrothenb SSC-Addicted Points: 427 More actions · Answer 9

DECLARE @test-2 TABLE (

EmpName VARCHAR(40) ,

BirthDate DATE

);

INSERT INTO @test-2 ( EmpName , BirthDate

)

VALUES ( '30 Yrs old yesterday' , DATEADD(day , -1 , DATEADD(year , -30 , GETDATE()))

) , ( '30 Yrs old today' , DATEADD(year , -30 , GETDATE())

) , ( '30 Yrs old tomorrow' , DATEADD(day , 1 , DATEADD(year , -30 , GETDATE()))

);

SELECT EmpName , BirthDate ,

CASE

WHEN DATEADD(YY , DATEDIFF(yy , BirthDate , GETDATE()) , BirthDate) < GETDATE()

THEN DATEDIFF(yy , BirthDate , GETDATE())

ELSE DATEDIFF(yy , BirthDate , GETDATE()) - 1

END AS Age

FROM @test-2;