Comments on: Why test ?

By: Blogroll Report 14/08/2009 – 21/08/2009 « Coskan’s Approach to Oracle

Blogroll Report 14/08/2009 – 21/08/2009 « Coskan’s Approach to Oracle — Mon, 07 Sep 2009 16:41:11 +0000

[...] 5- How to get the date for the last day of the previous month? Jonathan Lewis – Why test ? [...]

By: Raj

Raj — Mon, 31 Aug 2009 07:30:04 +0000

Jonathan,

There was similar type of question posted in Orafaq.com http://www.orafaq.com/forum/t/149542/73596/ I am posting it here because, I am not sure as to why the procedure was not failing for Michel or for me.

Can you please provide your invaluable advise on this?

Ps. I participate in that forum with my name as bonker.

By: Nigel

Nigel — Fri, 21 Aug 2009 08:56:08 +0000

So! You’ve met him! My favourite quote: “Execution Plan? That’s an index, right?”.

By: Jonathan Lewis

Jonathan Lewis — Thu, 20 Aug 2009 21:36:24 +0000

Was he also the developer who said: “We don’t have time to do it right – but we will have time to do it again ?”

By: Nigel

Nigel — Thu, 20 Aug 2009 08:59:31 +0000

I knew a developer who often said, “Testing? That means doing it all twice.”

By: William Robertson

William Robertson — Wed, 19 Aug 2009 07:35:18 +0000

Also here: http://oracle-wtf.blogspot.com/2006/02/stop-press-oracle-granted-license-to.html

By: Centinul

Centinul — Tue, 18 Aug 2009 23:34:06 +0000

This is noted in the SQL Reference: http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14200/functions004.htm#i76717

“If date is the last day of the month or if the resulting month has fewer days than the day component of date, then the result is the last day of the resulting month. Otherwise, the result has the same day component as date.”

By: richie

richie — Tue, 18 Aug 2009 22:26:36 +0000

I need to do this a lot and always last_day(add_months(sysdate,-1)) — can’t go wrong with that one.

By: Wolfgang Breitling

Wolfgang Breitling — Tue, 18 Aug 2009 21:47:20 +0000

add_months does not seem to suffer from the same problem:

SQL> select add_months(last_day(sysdate),-1) from dual;

ADD_MONTHS
———-
2009-07-31

1 row selected.

SQL> select add_months(last_day(sysdate),-2) from dual;

ADD_MONTHS
———-
2009-06-30

1 row selected.

SQL> select add_months(last_day(date ’2009-07-18′),-1) from dual;

ADD_MONTHS
———-
2009-06-30

1 row selected.

SQL>

By: Centinul

Centinul — Tue, 18 Aug 2009 18:58:01 +0000

I remember first realizing the implications of using the interval functions when reading Tom Kyte’s Expert Oracle Database Architecture. He highlights this issue on pages 526 and 527.

Thanks for reminding us all!