Have you tried 
SELECT TIME_DIFF(time_entry, time_exit)
  FROM entry_exit
 WHERE customer = 'SOME CUSTOMER';

[download]

In other words, did you even look at the MySQL manual? http://dev.mysql.com/doc/mysql/en/Date_and_time_functions.html

------
We are the carpenters and bricklayers of the Information Age.

Then there are Damian modules.... *sigh* ... that's not about being less-lazy -- that's about being on some really good drugs -- you know, there is no spoon. - flyingmoose

I shouldn't have to say this, but any code, unless otherwise stated, is untested

In reply to Re: MySql Timestamps by dragonchild
in thread MySql Timestamps by Agyeya

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