Index and Key

[anandknr]

Hi all,

A little confusion here.
1. What is the concept of keys in progress and how it differs from index. (gsdbe.pdf points about both)
2. Do we have any key constraints available (like foriegn key constraint) ?
3. Primary index accepts null value when i tested. (not as per gsdbe.pdf, chapter 1-6)

Regards,
ANand

 

[RealHeavyDude]

There are tons of literature on relational database design that can be found ...

• The concept of a key is part of the logical database design and an index is its physical, database specific implementation.
• On the ABL engine the Progress database does not support constraints.
• I've never tried to have NULL values in the primary index. I always have a business logic in place that prevents that in the first place - which is, IMHO, good practice as you don't want the user to see standard Progress error messages to which they usually can't relate. Therefore I can't comment on that. If I would need to speculate I would say that, according to documentation, it would be a bug. Other than that I would suggest to defined fields which appear in an index as mandatory.

Heavy Regards, RealHeavyDude.

 

[GregTomkins]

Not that they are a good thing, but IIRC, null values are the one and only way you can achieve duplicate index values within a primary key defined as unique.

 

[TomBascom]

Aside from bugs

 

[tamhas]

If the field is marked as Mandatory, null is not accepted. Some people think that is a bad thing, however.

 

[TomBascom]

What is "gsdbe.pdf"? And where might one find it?

 

[tamhas]

gs = getting started
dbe =? database essentials

 

[Stefan]

What is "gsdbe.pdf"? And where might one find it?

http://communities.progress.com/pcom/docs/DOC-107363

http://documentation.progress.com/output/OpenEdge110/pdfs/gsdbe/gsdbe.pdf

 

[TomBascom]

Thanks guys. The original reference didn't ring any bells -- now I know what it is.