| Trigger sum constraints [message #446276] |
Sun, 07 March 2010 07:45  |
cronin
Messages: 2
Registered: March 2010
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Junior Member |
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First of all, I'm very new to oracle and sql in general so this question may be obvious, impossible, or anywhere in between.
Basically, I need to fulfil the constraint:
"student cannot have more than 100 points"
I'm pretty sure I need to use a trigger to do this, but I don't understand how this would work.
Written in plain english I imagine it work work something like:
AFTER UPDATE
WHERE student.lessonid = lesson.lessonid
IF SUM(lesson.points) > 100 then ROLLBACK
lessonid is the only field relating the two tables.
--
Again, I apologise if this is a daft question, I hope someone can at least point me in the right direction to being able to fulfil that criteria, whether it be using triggers or not.
Thanks!
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| Re: Trigger sum constraints [message #446277 is a reply to message #446276] |
Sun, 07 March 2010 08:03  |
gkrishn
Messages: 506
Registered: December 2005
Location: Putty a dark screen
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Senior Member |
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why dont you write it in a plsql block.
if (your condition)
then
exit;
end if;
you can even create within a procedure or function.
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| Re: Trigger sum constraints [message #446288 is a reply to message #446276] |
Sun, 07 March 2010 09:11 |
cronin
Messages: 2
Registered: March 2010
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Junior Member |
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My apologies for not being clear, the student should be able to take more than one lesson (each lesson is a maximum of 20 points), summing up to a total of <= 100.
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