Re: Calculate next event date based on instance of the day of week

Hello,
> I have a table which stores an event date. The event is stored as a
> standard mm/dd/yy entry.
>
> I then need to calculate based on the dd value, WHICH day of the
> week that is (e.g. Wednesday) and which occurrence of that day of
> the week, within the month, it is (e.g. the THIRD Wednesday).
>
Here is an example to reach this far ....

postgres=# create table mt(myd date);
postgres=# insert into mt select current_date+se from (select
generate_series(1,10000) as se ) as x;
postgres=# select * from mt order by
postgres-# myd limit 10;
myd
------------
2010-12-04
2010-12-05
2010-12-06
2010-12-07
2010-12-08
2010-12-09
2010-12-10
2010-12-11
2010-12-12
2010-12-13
(10 rows)

This is the query to get the data in the format you want...

select myd, d ,w from (
select myd, to_char(myd,'Day') as d , to_char(myd,'W') as w ,rank() over
(partition by to_char(myd,'W') order by myd ) as x from mt order by myd
) as t order by myd ;

myd | d | w
------------+-----------+---
2010-12-04 | Saturday | 1
2010-12-05 | Sunday | 1
2010-12-06 | Monday | 1
2010-12-07 | Tuesday | 1
2010-12-08 | Wednesday | 2
2010-12-09 | Thursday | 2
2010-12-10 | Friday | 2
2010-12-11 | Saturday | 2
2010-12-12 | Sunday | 2
2010-12-13 | Monday | 2
2010-12-14 | Tuesday | 2
2010-12-15 | Wednesday | 3
2010-12-16 | Thursday | 3
2010-12-17 | Friday | 3
2010-12-18 | Saturday | 3
2010-12-19 | Sunday | 3
2010-12-20 | Monday | 3
2010-12-21 | Tuesday | 3
2010-12-22 | Wednesday | 4
2010-12-23 | Thursday | 4
2010-12-24 | Friday | 4
2010-12-25 | Saturday | 4
2010-12-26 | Sunday | 4
2010-12-27 | Monday | 4
2010-12-28 | Tuesday | 4
2010-12-29 | Wednesday | 5
2010-12-30 | Thursday | 5
2010-12-31 | Friday | 5

Regards,
Jayadevan

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