Re: Date manipulation

Mark,

> How does one perform date manipulation within SQL? For example, SQL
> Server has a dateadd() function that takes a date part, scalar, and
> the
> date to manipulate.

As I have remarked before, such functions as DATEADD are unnecessary in
PostgreSQL because PostgreSQL has a proper implementation of Date data
types, unlike MS SQL Server. Thus, to add to a date:

new_date := old_date + INTERVAL('1 week');

Or to subtract:

break_time := restart_time - stop_time;

It's improtant to remeber that the differnence of two dates or times is
an interval, and while you can add an interval to a date you cannot add
two dates.

Additionally, if you browse to Roberto Mello's PG/plSQL function library
(see link for the PostgreSQL.org web site) you will find an extension to
the OVERLAPS function that I find quite useful (I should, I wrote it!).

-Josh

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