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
------------2010-12-042010-12-052010-12-062010-12-072010-12-082010-12-092010-12-102010-12-112010-12-122010-12-13
(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  | 12010-12-05 | Sunday    | 12010-12-06 | Monday    | 12010-12-07 |
Tuesday  | 12010-12-08 | Wednesday | 22010-12-09 | Thursday  | 22010-12-10 | Friday    | 22010-12-11 | Saturday  |
22010-12-12| Sunday    | 22010-12-13 | Monday    | 22010-12-14 | Tuesday   | 22010-12-15 | Wednesday | 32010-12-16 |
Thursday | 32010-12-17 | Friday    | 32010-12-18 | Saturday  | 32010-12-19 | Sunday    | 32010-12-20 | Monday    |
32010-12-21| Tuesday   | 32010-12-22 | Wednesday | 42010-12-23 | Thursday  | 42010-12-24 | Friday    | 42010-12-25 |
Saturday | 42010-12-26 | Sunday    | 42010-12-27 | Monday    | 42010-12-28 | Tuesday   | 42010-12-29 | Wednesday |
52010-12-30| Thursday  | 52010-12-31 | Friday    | 5
 


Regards,
Jayadevan





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