Jesse,
>BTW, is there a way to change this function so that it does away with the
>"today" variable, and uses a field from a different database? For
instance,
>I have CampStartDate stored on the Config table. Can this Age function
>be modified to get the "today" variable from that table instead?
For flexibility's sake, it may be preferable to pass the column value to
the function as 'today', but if you want to tie the function to that one
column value, just move the today declaration to inside the func and
have the func do something like (untested)...
CREATE FUNCTION Age( dob DATE ) RETURNS INTEGER
DETERMINISTIC
BEGIN
DECLARE today DATE;
SELECT CampStartDate INTO today FROM config;
RETURN DATE_FORMAT(FROM_DAYS(TO_DAYS(today) - TO_DAYS(dob)), '%Y') + 0;
END;
You could do the same with 'dob'.
PB
Jesse wrote:
BTW, is there a way to change this function so that it does away with
the "today" variable, and uses a field from a different database? For
instance, I have CampStartDate stored on the Config table. Can this
Age function be modified to get the "today" variable from that table
instead?
Thanks,
Jesse
----- Original Message ----- From: "Peter Brawley"
<[EMAIL PROTECTED]>
To: "Jesse" <[EMAIL PROTECTED]>
Cc: "MySQL List" <mysql@lists.mysql.com>
Sent: Wednesday, December 28, 2005 10:20 AM
Subject: Re: Need Help Writing a Trigger
Jesse,
>Therefore, instead of putting that long calculation in my query every
time,
>I'm looking for a simpler solution, a more automatic one.
CREATE FUNCTION Age( dob DATE, today DATE ) RETURNS INTEGER
DETERMINISTIC
BEGIN
RETURN DATE_FORMAT(FROM_DAYS(TO_DAYS(today) - TO_DAYS(dob)), '%Y') + 0;
END;
PB
-----
Jesse wrote:
It's not as simple as that. First, if you subtract the curdate()
from the birthday (or vice versa), you end up with some large number
that isn't the actual age at all. So, the calculation is a bit more
complicated than that.
Also, I'm not interested in their current age, but their age at the
time of camp, which means that I need to pull a date from a config
file. Therefore, instead of putting that long calculation in my
query every time, I'm looking for a simpler solution, a more
automatic one.
Jesse
----- Original Message ----- From: "Jesse" <[EMAIL PROTECTED]>
To: "MySQL List" <mysql@lists.mysql.com>
Sent: Tuesday, December 27, 2005 4:34 PM
Subject: Need Help Writing a Trigger
I'm trying to write a trigger that will update the age of a camper
when ever a record is updated or inserted. I have a table named
Campers which contains basic information about the camper as well
as their birthday. I have another table named Config which holds
various settings, including the date at which camp begins. The Age
field in the Campers table needs to be set based on the
Config.CampStartDate. So, I have the following query that does
what I need:
SELECT c.lastname,c.firstname,c.birthday,
(Year(co.CampStartDate)-Year(c.Birthday)) -
(Right(co.CampStartDate,5)<Right(c.Birthday,5)) As Age
from campers c, config co
(there is always only one record in config).
There are actually a few options here:
1. Create a trigger that updates this field when new records are
inserted or updated. This will keep the field updated.
2. Everywhere in my code where I need the age, I insert the
calculation above to include an age column.
3. I write a view that includes this calculation in it and just
use that everywhere. However, I don't know if there are any
performance issues with Views or anything.
First, what is the best approach here? Also, if I can get the
trigger to work, how do I write it? I've gotten this far with it:
CREATE TRIGGER insUpdAge BEFORE INSERT ON Campers
FOR EACH ROW
BEGIN
// somehow i need to get the CampStartDate out of the Config
table, and store it in a variable (I think).
// next, I need to do an set new.age=(calculated age).
END
Can anyone give me a hand here?
Thanks,
Jesse
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