RE: Implicitly hidden column & EXTNAME D/S

In this rare case, yes I do need every column. I can't recall the last time I wanted a SELECT *. Virtually all the time, it's a subset of columns from one or more tables.

Assuming EXTNAME and SELECT * handled implicitly hidden columns the same, I'm not sure any future table layout changes would cause a problem. The compiler would see the same columns for both EXTNAME and SELECT *.

Thanks



-----Original Message-----
From: Birgitta Hauser [mailto:Hauser@xxxxxxxxxxxxxxx]
Sent: Friday, May 01, 2020 1:18 PM
To: 'RPG programming on IBM i' <rpg400-l@xxxxxxxxxxxxxxxxxx>
Subject: RE: Implicitly hidden column & EXTNAME D/S

Do you really need all columns in your programs or only a sub-set?
I assume in 99% of all cases you only need a sub-set.
If you list your columns, you do not have to recompile if your table is changed, i.e. you only have to recompile or change where you use the new/changed field.
With a list of data the query optimizer might be able to perform a IOA (Index Only Access), i.e. finds an index where all information you request can be found within the key values. In this way there is no need to access the table data themselves..

Mit freundlichen Grüßen / Best regards

Birgitta Hauser


"Shoot for the moon, even if you miss, you'll land among the stars." (Les
Brown)
"If you think education is expensive, try ignorance." (Derek Bok) "What is worse than training your staff and losing them? Not training them and keeping them!"
"Train people well enough so they can leave, treat them well enough so they don't want to." (Richard Branson)