Re: diary constraints

On 8/23/05, Gary Stainburn <gary(dot)stainburn(at)ringways(dot)co(dot)uk> wrote:
>
> Hi folks
>
> I know this has been discussed in the past, but no amount of keywords
> has returned anything from the archives.
>
> I want to create a courtesy car diary diary system where I have a table
> containing all of the cortesy cars in the pool, and then an allocation
> table which has two timestamps, one for the start date/time and one for
> the return date/time.
>
> How do I go about creating constraints on inserts and updates to ensure
> that
>
> a) the finish is after the start

check constraint like -> "finish_time > start_time" this will do

b) two allocations for a single vehicle don't overlap.

Use "overlaps" function in a trigger to validate the above.

--
> Gary Stainburn
>
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--
with regards,
S.Gnanavel
Satyam Computer Services Ltd.