将 DATEDIFF 与 ALTER TABLE 一起使用的问题

Question

I'm trying to add a computed column into an existing database table that will calculate age eg "23" from field "DOB" stored as YEAR (4) eg 1988.

Using the below, I get a

1582 error - an incorrect parameter count in the call to native function 'DATEDIFF'.

ALTER TABLE names ADD Age INT GENERATED ALWAYS AS (DATEDIFF('year', DOB, CURDATE))

Many examples I've found online have similar layout in terms of parameter count (some use GETDATE or NOW instead of CURDATE).

Anyone have any idea what I'm doing wrong?

Answer 1

Thanks to RigsFolly & Barmar for the feedback. I made a fresh cup of tea and looked at it again.

With DATEDIFF, it seems the MYSQL Server syntax can use the datepart and then use two dates to calculate (including GETDATE). I'm using MySQL through myphp admin which doesnt seem to like the datepart.

I dropped the datepart and changed the date format of the stored DOB field from "YEAR" to "DATE". As a result I no longer received the parameter error and by default the output of the DATEDIFF was returned in days. I then divided the output by 365 to get years.

My original order was wrong too which gave me the DATEDIFF output as a negative value, so changed the order and it works a charm. Thank you.

ALTER TABLE names ADD Age INT GENERATED ALWAYS AS (DATEDIFF(CURDATE(), DOB) / 365);