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 Random Date Generator

Author  Topic 

Yak Posting Veteran

60 Posts

Posted - 2006-05-11 : 07:42:05
I need to generate some random data - 1000 people and their dates of birth (I want people aged 1 day to 90 years).
Random names were easy from lists of firstnames and surnames.
Random dates seem to be much harder. The only way that I have been able to do it is by generating random years, concatenated with random months, and random days. All converted to the DATETIME datatype.
This is really messy because I need to account for the correct number of days per month so that I don't generate nonsense dates e.g. 31/02/1970 (No apologies for using the CORRECT (UK) date format;-))
Is there anything I can do that utilises GETDATE()?
Ideas? ...better still a ready-made function/stored proc!

Sorry if this topic has already been covered, but I couldn't find it when I searched the forums.

In (Som, Ni, Yak)

17689 Posts

Posted - 2006-05-11 : 07:57:14
select DOB, datediff(year, DOB, getdate())
select dateadd(month, -1 * abs(convert(varbinary, newid()) % (90 * 12)), getdate()) as DOB
) d


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Arnold Fribble
Yak-finder General

1961 Posts

Posted - 2006-05-11 : 08:00:16
How does

DATEADD(day, DATEDIFF(day, 0, GETDATE()) - 1 - FLOOR(RAND(CAST(NEWID() AS binary(4))) * 365.25 * 90), 0)

grab you?
I wouldn't be keen on the completely flat distribution of dates, myself, but it's probably good enough for most demo purposes.
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Michael Valentine Jones
Yak DBA Kernel (pronounced Colonel)

7020 Posts

Posted - 2006-05-11 : 08:46:11
This will generate as many random dates as you want.

Function F_TABLE_NUMBER_RANGE is available here:

[DATE] =
-- Get random dates in last 90 year starting from today
rnd =
-- Get random integer
-- Modulus by number of days in last 90 years
-- to get a date offset from present
-- Function in script library forum
) a

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Yak Posting Veteran

60 Posts

Posted - 2006-05-11 : 09:02:57
Thanks to you all. Just what I needed.
I agree that the distribution of dates is probably unrealistic but this is fine for my purposes.
Most importantly....MUCH less code than I had written.
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Master Smack Fu Yak Hacker

2052 Posts

Posted - 2006-05-12 : 03:13:13
Rather sacreligiously I used Excel to do this. Generated a random number and formatted it as a date, you can also set an upper and lower bound for the number



Oh, so they have internet on computers now!
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Yak Posting Veteran

60 Posts

Posted - 2006-05-12 : 11:31:48
Good idea Steve. Had I thought of it, I would have done the same thing. I've often spent time creating stored procedures and functions in SQL Server,rather than going for a quick solution using other software, just so that 'I can use them again one day'. Have I used most of them again?...No!
Thanks for your input.
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