Interview › Age from a date

SQL interview: age in years from a date of birth

DATEDIFF(year, dob, today) counts year boundaries, not birthdays.

Prompt. Age in completed years as of today.

Hint: DATEDIFF then subtract if the anniversary is still ahead

Your T-SQL

SELECT customer_id, dob,
       DATEDIFF(year, dob, CAST(GETDATE() AS date))
       - CASE WHEN DATEADD(year, DATEDIFF(year, dob, CAST(GETDATE() AS date)), dob)
                   > CAST(GETDATE() AS date)
              THEN 1 ELSE 0 END AS age
FROM Customers;

Do not use this for anything legal without a test table of leap-day births.

Then write it on a ticket

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