RE: SQL date comparison - a better way?

midrange-l-request@xxxxxxxxxxxx wrote:

>   3. RE: SQL date comparison - a better way? (rob)
>
>  And, providing your applications do not directly access 
>the physical file, but only access the logical files, you could add fields 
>without any level checks.
>
>I've seen this technique used by a software vendor.

I've used the technique with good results although there are a couple items to 
be aware of.

Most importantly, the LFs must be compiled with explicit field lists. Add a new 
field to the PF and recompile it. The previous LFs can then be recompiled and 
will not cause level-checks as long as the field lists are unchanged and no 
significant changes were made to the original fields. New fields shouldn't need 
to be added at the end of the PF; they can be anywhere -- the original physical 
order can even change.

Also, there generally needs to be at least one program that is recompiled 
because this program is the one that does the physical updates. When new fields 
get added to a table, they ought to be accounted for in the primary physical 
maintenance program. This program would always need to be compiled over the 
actual PF. While it's certainly possible to have an LF defined for this 
purpose, the problem remains the same. If data in the new fields will be 
maintained, the update program needs to include the fields. Ideally, this will 
only be a single program (or module or service program procedure or...). In a 
lot of circumstances, this might be minimized by using default values for the 
new fields.

Tom Liotta

-- 
Tom Liotta
The PowerTech Group, Inc.
19426 68th Avenue South
Kent, WA 98032
Phone  253-872-7788 x313
Fax    253-872-7904
http://www.powertechgroup.com


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