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sql server (alternate) : Intensively used function in view needs a minimum and maximum from a table


hdenooijer NO[at]SPAM hotmail.com
12/30/2004 2:38:51 AM
I have a problem (who not?) with a function which i'm using in a view.
This function is a function which calculates a integer value of a
date. For example: '12/31/2004 00:00:00" becomes 20041231. This is
very handy in a datawarehouse and performes superfast. But here is my
problem.

My calendar table is limited by a couple of years. What happens is
that sometimes a value is loaded which is not in the range of the
Calendardate. What we want to do is when a date is loaded is that this
function insert a minimum date when date < minimum date and a maximum
date when date > maximum date.

Yes i know you're thinking : This is datamanipulation and yes this is
true. But now we loose information in our cubes and reports by inner
joining. So if we can use a minimum and a maximum than a user would
say: "This is strange, a lot of values on 1980/1/1!" instead of "I
think that i have not all the data!"

Greetz

John Bell
12/30/2004 11:56:22 AM
Hi

If you LEFT or RIGHT JOIN to the calendar table you will get a NULL value
for the column, you can then is CASE to determine the value

CREATE FUNCTION ConvertDate (@datevalue datetime)
RETURNS INT
AS
BEGIN
DECLARE @dateint INT
SELECT @dateint = CAST( CASE WHEN A.Date < '20030101' THEN '19800101'
WHEN A.Date > '20051231' THEN '99991231'
ELSE CONVERT(CHAR(4),C.[Year]) + RIGHT('0'+
CONVERT(VARCHAR(2),C.[Month]),2) + RIGHT('0'+ CONVERT(VARCHAR(2),C.[Day]),2)
END AS INT )
FROM ( SELECT @datevalue AS [Date] ) A
LEFT JOIN CALENDAR C ON C.[Date] = A.[Date]
RETURN @dateint
END
GO

John

[quoted text, click to view]

Hugo Kornelis
12/31/2004 12:33:10 AM
[quoted text, click to view]
(snip)

Hi Hennie,

Is this conversion all that your function does? If so, you might want to
try the following alternative (using CURRENT_TIMESTAMP as example; replace
it with your date column / parameter):

SELECT CAST(CONVERT(varchar, CURRENT_TIMESTAMP, 112) AS int)

You could put this in the UDF (probably at least as fast as your current
Calenmdar-table based function), or use it inline as a replacement to the
function call (probably even faster).

It should work for all dates from Jan 1st 1753 through Dec 31st 9999.

Best, Hugo
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