Diffrence in days in two dates

[natasha_sharma]

Hi,

 

I want to update a column in my table with the difference between two dates. resultdate  variable is in yyyy-mm-dd

update table test_table set days_diff = (resultdate - CURDATE()) where 1 = 1;

So, i want to reset my days_diff variable with the latest date when the code is run.

 

But this code is given me correct days difference in first run, but when i instantly run this code, I get wrong number of differences.

 

Is there any better code to to do this ?

Edited March 15, 2016 by natasha_sharma

[Barand]

You need to use the DATEDIFF() function

 

http://dev.mysql.com/doc/refman/5.6/en/date-and-time-functions.html#function_datediff

 

but the best way to do it is not to do it at all.

 

Derived data should not be stored in your database. Calculate it when required instead of continually updating the table.