Question

I want to restrict to user when he enters start and end date between already present start and end dates in the following table.

For example: user tries to insert date start date 2/6/2012 and end date 4/6/2012; this date comes between event e2 from the table below so the user is not allowed to insert it.

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 id               event               startdate    enddate
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 11                e1                 31/5/2012    1/6/2012
 12                e2                 1/6/2012     4/6/2012
 13                e3                 5/6/2012     6/6/2012
 14                e4                 15/6/2012    16/6/2012

I want to find a count of those events that conflict with other events.

Answer 1

select tbl.startdate, count(tbl.startdate)
from YourTable tbl
where 
exists(select * from YourTable tbl2 where ((tbl2.startdate>=tbl.startdate AND tbl2.startdate<=tbl.enddate) OR (tbl2.enddate>=tbl.startdate AND tbl2.enddate<=tbl.enddate)))
group by tbl.startdate