Solved

T-SQL: calculating person age

Posted on 2013-11-01
3
1,440 Views
Last Modified: 2013-11-19
One table column has Date of Birth.
I have to calculate person's age in  years, for example 1.23 ,  8.35 , 37.36 etc. in another column.
Any thoughts on this?
0
Comment
Question by:quasar_ee
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
3 Comments
 
LVL 11

Accepted Solution

by:
Simone B earned 250 total points
ID: 39617946
DATEDIFF returns an integer, so you have to cast or convert to a decimal. If you use 365.25 days per year instead of 365, that will cover for the leap years. Then to round the whole thing to 2 decimal places, cast again:

SELECT CAST(CAST(DATEDIFF(d,YourDateField,GETDATE()) AS DECIMAL(10,2))/365.00 AS DECIMAL(10,2))
0
 
LVL 92

Expert Comment

by:Patrick Matthews
ID: 39619158
Buttercup1,

I like it, but I see a couple of problems, such as:
In either formula, having two decimal places is not enough precision, and
In the 365.25 formula, you have a risk that you will understate the true age in some edge cases

Illustrating the first, consider this example:

DECLARE @dob datetime = '2012-02-28',
    @today datetime = '2013-02-27'
    
SELECT CAST(CAST(DATEDIFF(d, @dob, @today) AS DECIMAL(10, 2)) / 365.00 AS DECIMAL(10, 2)) AS _365,
    CAST(CAST(DATEDIFF(d, @dob, @today) AS DECIMAL(10, 2)) / 365.25 AS DECIMAL(10, 2)) AS _36525

Open in new window


This returns 1.00 and 1.00, respectively, yet most people would agree that this person is not yet a year old.  Using only two digits for the decimal portion is not precise enough.  Using decimal(10, 4) instead would remedy that.

Now consider how using 365.25 can understate the age in some edge cases.  (I am adopting the more precise decimal(10, 4) here.)

DECLARE @dob datetime = '2013-02-28',
    @today datetime = '2014-02-28'
    
SELECT CAST(CAST(DATEDIFF(d, @dob, @today) AS DECIMAL(10, 4)) / 365.00 AS DECIMAL(10, 4)) AS _365,
    CAST(CAST(DATEDIFF(d, @dob, @today) AS DECIMAL(10, 4)) / 365.25 AS DECIMAL(10, 4)) AS _36525

Open in new window


The "365" formula returns 1.0000, and the "365.25" formula returns 0.9993, but everyone would agree that such a person should be counted as one year old.

:)

Patrick
0
 
LVL 92

Assisted Solution

by:Patrick Matthews
Patrick Matthews earned 250 total points
ID: 39619233
Inelegant, and there may well be a better way, but this does address the points I made above:

SELECT 
    DOB, GETDATE(),
    DATEADD(year, DATEDIFF(year, DOB, GETDATE()), DOB),
    DATEADD(year, DATEDIFF(year, DOB, GETDATE()) - 1, DOB),
    CASE 
    WHEN CONVERT(date, DATEADD(year, DATEDIFF(year, DOB, GETDATE()), DOB)) > CONVERT(date, GETDATE()) THEN
        CONVERT(decimal(10, 4), DATEDIFF(year, DOB, GETDATE()) - 1) + 
        CONVERT(decimal(10, 4), DATEDIFF(day, DATEADD(year, DATEDIFF(year, DOB, GETDATE()) - 1, DOB), GETDATE())) / 
        CONVERT(decimal(10, 4), DATEDIFF(day, DATEADD(year, DATEDIFF(year, DOB, GETDATE()) - 1, DOB), DATEADD(year, DATEDIFF(year, DOB, GETDATE()), DOB)))
    WHEN CONVERT(date, DATEADD(year, DATEDIFF(year, DOB, GETDATE()), DOB)) < CONVERT(date, GETDATE()) THEN
        CONVERT(decimal(10, 4), DATEDIFF(year, DOB, GETDATE())) +
        CONVERT(decimal(10, 4), DATEDIFF(day, DATEADD(year, DATEDIFF(year, DOB, GETDATE()), DOB), GETDATE())) / 
        CONVERT(decimal(10, 4), DATEDIFF(day, DATEADD(year, DATEDIFF(year, DOB, GETDATE()), DOB), DATEADD(year, DATEDIFF(year, DOB, GETDATE()) + 1, DOB)))
    ELSE
        CONVERT(decimal(10, 4), DATEDIFF(year, DOB, GETDATE()))
    END AS Age
FROM SomeTable

Open in new window

0

Featured Post

Edgartown IT Case Study

Learn about Edgartown's quest to ensure the safety and security of the entire town's employee and citizen data. Read the case study!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Use SSRS to email customers? 4 30
Need split for SQL data 7 50
learning MS SSIS 13 24
Access - convert query for SQL Server 5 12
This article explains how to reset the password of the sa account on a Microsoft SQL Server.  The steps in this article work in SQL 2005, 2008, 2008 R2, 2012, 2014 and 2016.
This article shows gives you an overview on SQL Server 2016 row level security. You will also get to know the usages of row-level-security and how it works
Using examples as well as descriptions, and references to Books Online, show the documentation available for date manipulation functions and by using a select few of these functions, show how date based data can be manipulated with these functions.
This videos aims to give the viewer a basic demonstration of how a user can query current session information by using the SYS_CONTEXT function

752 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question