SQLite: How to calculate age from birth date

Question

What is the best way to calculate the age in years from a birth date in sqlite3?

Answer 1

I have spent whole my Weekend on this Topic and created this Query.

SELECT ID,
       Name,
       InitialDate,
       LastDate,
       CASE 
           WHEN strftime('%m', LastDate) > strftime('%m', InitialDate) THEN strftime('%Y', LastDate) - strftime('%Y', InitialDate) 
           WHEN strftime('%m', LastDate) < strftime('%m', InitialDate) THEN strftime('%Y', LastDate) - strftime('%Y', InitialDate) - 1 
           WHEN strftime('%m', LastDate) = strftime('%m', InitialDate) THEN 
           CASE 
               WHEN strftime('%d', LastDate) >= strftime('%d', InitialDate) THEN strftime('%Y', LastDate) - strftime('%Y', InitialDate) 
               ELSE strftime('%Y', LastDate) - strftime('%Y', InitialDate) - 1 
           END 
       END AS Years,
       CASE
           WHEN strftime('%m', LastDate) == strftime('%m', InitialDate) THEN
               CASE
                   WHEN strftime('%d', LastDate) == strftime('%d', InitialDate)    THEN ( strftime('%m', LastDate) - strftime('%m', InitialDate) ) -- i.e., 0
                   WHEN strftime('%d', LastDate) > strftime('%d', InitialDate)     THEN ( strftime('%m', LastDate) - strftime('%m', InitialDate) ) -- i.e., 12
                   WHEN strftime('%d', InitialDate) > strftime('%d', LastDate)     THEN (strftime('%m', LastDate) - strftime('%m', InitialDate)) + 11 -- i.e., 11
               END
           WHEN strftime('%m', LastDate) > strftime('%m', InitialDate) THEN 
               CASE
                   WHEN strftime('%d', LastDate) == strftime('%d', InitialDate)    THEN strftime('%m', LastDate) - strftime('%m', InitialDate)
                   WHEN strftime('%d', LastDate) > strftime('%d', InitialDate)     THEN strftime('%m', LastDate) - strftime('%m', InitialDate)
                   WHEN strftime('%d', InitialDate) > strftime('%d', LastDate)     THEN ( strftime('%m', LastDate) - strftime('%m', InitialDate) ) - 1
               END
           WHEN strftime('%m', InitialDate) > strftime('%m', LastDate) THEN
               CASE 
                   WHEN strftime('%d', LastDate) == strftime('%d', InitialDate)    THEN 12 - ( strftime('%m', InitialDate) - strftime('%m', LastDate) )
                   WHEN strftime('%d', LastDate) > strftime('%d', InitialDate)     THEN 12 - ( strftime('%m', InitialDate) - strftime('%m', LastDate) )
                   WHEN strftime('%d', InitialDate) > strftime('%d', LastDate)     THEN 11 - (strftime('%m', InitialDate) - strftime('%m', LastDate))
               END           
       END AS Months,
       CASE 
           WHEN strftime('%d', LastDate) == strftime('%d', InitialDate)    THEN 0
           WHEN strftime('%d', LastDate) > strftime('%d', InitialDate)     THEN strftime('%d', LastDate) - strftime('%d', InitialDate)
           WHEN strftime('%d', InitialDate) > strftime('%d', LastDate)     THEN ( strftime('%d', date(InitialDate, 'start of month', '+1 month', '-1 day') ) - strftime('%d', InitialDate) + strftime('%d', LastDate) )
            
   END AS Days
  FROM tbl_Dates;

Tested on a Data Set consist of 248 Records. Years and Months are with calculated 100% Accuracy. While Days are 124 out of 248 Records are with Difference of ±1 Day(s). I would request other Genius Minds to Dig out and find the remaining solution. For me Its OK and working 100% Fine.